0. Abstract

In this thesis I propose a disjoint theory of humor, a departure from traditional theories which seek to rigidly define all instances of the phenomena in one fell swoop. The theory is presented with an eye towards the development of a computer program which might eventually be able to identify and generate humorous sentences. This project has been carried out in the overall context of the questions 'How do people create?' and the related 'Could a machine be taught to create?'. It is my view that the domain of 'humor' may be extremely useful in the search for the answers to these questions.

1. Introduction

"Analyzing humor is like dissecting a frog. Few people are interested in it and the frog dies of it."

—E. B. White

The mental processes that fall under the heading of creativity have remained elusive for thousands of years. In ancient times many cultures considered poets, musicians, artists and orators to be divinely inspired1, suggesting that creativity has always been considered mysterious and revered. Nowadays, such success might be attributed to inspiration and intuition, terms that are about as informative as "prophecy" when it comes to explaining how creativity works. Before we can address the questions concerning the generation of creative ideas, it will be helpful to attempt a definition of this seemingly intuitive concept, and answer the question What is creativity?

In its traditional sense, creativity is identified with creation ex nihilo, or in other words, the act of generating something out of nothing. This notion seems difficult to apply to the creation of ideas, since all human creators are equipped with a vast compendium of knowledge, and new ideas are not created in a vacuum. A creative idea must be novel, and Margaret Boden2 distinguishes between psychological creativity, where an idea is novel to the individual, and historical creativity, where an idea is novel for the human race. She points out that all historical creativity depends upon psychological creativity, so an explanation of psychological creativity must necessarily explain historical creativity as well. Is novelty enough for an idea to be considered creative?

We might suggest that a creative idea must be interesting, as well as novel, but this requirement seems arbitrary, considering the varying standards of what people find interesting. We would not want to discredit the creative handiwork of plumbers or mechanics simply because some psychologist does not find their work interesting. On the other end of the spectrum, some academics have found the decidedly mundane to be extremely interesting. Consider Noam Chomsky's observation that virtually all speech acts should be viewed as creative, since most sentences that we utter are psychologically, if not historically, novel. Considering his specialty, it is no surprise that Chomsky finds the formation of grammatical sentences interesting, but at first glance, it seems as if no analysis of the concept will decisively settle what is interesting.

What we can hope for is a systematic investigation of the various activities generally grouped under the heading of creativity, which will provide us with a basis for categorizing these activities as a function of the way that they work. In many ways, creativity is currently used as a catch all phrase to "explain" activities ranging from problem solving and theorizing to painting and improvising. Perhaps these activities have little in common save for the fact that, for most, we have no robust model of their workings. Or, perhaps these activities do share certain essential properties, such as the three that Philip Johnson-Laird has proposed: "(1) The result is formed from existing elements, but in a combination that is novel for the individual and perhaps society as a whole. It is not merely perceived or remembered. (2) It satisfies a pre-existing criteria. (3) It is not constructed by rote or derived by some simple deterministic procedure. The process allows for freedom of choice."3

The difficulty in producing creativity on demand may partially account for many researchers' lopsided focus on a few paradigmatic case studies involving historical geniuses, whose work is indisputably creative. Some drawbacks in studying the works of great geniuses include the relative scarcity of fresh data and the mythological nature of many of the accounts. Also, the value of phenomenological descriptions is unclear, since we have no reliable method for assessing the accuracy of introspection, and furthermore, many creative processes may be unconscious. Given these considerations, it may be fruitful to turn to mundane instances of creativity in the hopes of studying examples which are plentiful and relatively easy to generate.

One area of creativity which has received relatively little attention from scholars, despite its importance in everyday life, is the domain of humor and wit. A notable exception to this scholarly abstention is Arthur Koestler, whose work The Act of Creation emphasized the fundamental similarities between the creative mechanisms involved in art, science, and humor. Although his conclusions regarding the universal role of biassociation in creativity have been sharply criticized4, his strategy of treating humor as a Trojan Horse which can be used to infiltrate the citadel of creativity is still an exciting and promising prospect.

That the Jester should be brother to the Sage may sound like blasphemy, yet our language reflects the close relationship: the word 'witticism' is derived from 'wit' in its original sense of ingenuity, inventiveness. Jester and savant must both 'live on their wits'; and we shall see that the Jester's riddles provide us with a useful back-door entry, as it were, into the inner workshop of creative originality.5

Koestler felt that humor could provide a back-door for the study of creativity because "it is the only domain of creative activity where a complex pattern of intellectual stimulation elicits a sharply defined response in the nature of a physiological reflex."6 Furthermore, there are more recognized comic geniuses than scientific geniuses because more people are trying to be funny than to solve contemporary scientific problems. As such, the relative abundance of comic genius compared to scientific genius also contributes to the advantage of studying creativity as expressed in the form of comedy. Koestler's argument for the similarities between artistic, scientific, and comedic creativity provides plenty of motivation for the serious study of the domain of humor. No doubt, there is much to be learned from the study of humor that transcends the subject and can be directly applied to our understanding of other creative mental activities.

Part I:

2. What Are You Laughing At?

The domain of verbal humor is a subset of the natural language generation problem, since all verbal jokes are members (not always grammatical) of the language(s) in which they are told. However, a good joke or a witty saying is far less frequent than an ordinary grammatical sentence, although some people certainly have more of a knack for it than others. Since virtually all people have a sense of humor (or, at least, like to think that he does) a question central to the study of creativity immediately arises. Do really good comedians think in qualitatively different ways from the average wise guy, or do they just employ the same mechanisms as everybody else, only better? This question has been posed many times concerning different areas of creativity, and an analysis of wit will contribute to this dialogue. With careful attention to detail, wit and other domains of creativity will mutually shed light upon one another, suggesting new directions of research that will further illuminate human cognition.

Even before we worry about what makes a sentence witty, the problem of wit can be divided into two categories: (a) the generation of a joke (b) the comprehension of a joke. While these two tasks both seem to be involved in the creation of a joke, a listener's task is to understand and "get" the joke, two components of comprehension which may not be distinct. At first glance, the comprehension of a joke might not sound like a creative project, however the comprehension of many jokes and witty sayings can be viewed as a problem solving task, in which the goal is to figure out the humorous content of the sentence. This process often involves exploring various associative paths, such as opposition of ideas or similarity of sound, in a manner that might mirror the generative procedure that the writer followed. In certain respects, comprehension can be viewed as the inverse process of generation, since generation is the discovery of a problem for the listener to solve.

Both the production and comprehension of humor must depend upon knowledge of what is funny, and the question of 'what is funny?' is one that humanity has yet to completely answer. This knowledge need not be explicit in the minds of the participants; however, it must be represented at some level in order for individuals to recognize jokes and evaluate their funniness. The comic uses this judgment in the creation of the joke, to separate the wheat from the chaff, while the listener uses this judgment to respond to the joke. Of course, humor is a multi-faceted phenomenon, and no one theory has managed to encapsulate and explain it entirely (although some have claimed to).

In the following chapters, I will attempt to develop a theory of humor whose approach is markedly different from the theories that precede it. In order to determine which things are funny, I have essentially split the problem into figuring out how things are funny and why things are funny. The split is not a clean one, and the answers to these two questions overlap significantly.

In conceptualizing this split, it is helpful to review a lesson attributed to David Marr on the topic of levels of explanation:

To solve any [cognitive] problem, we must bear in mind a lesson from computation: we need at least three different levels of explanation. We need a theory of what is computed - what the input to the process is, what has to be recovered from it, and what constraints may guide the process. We need a theory of how the system carries out the computations, that is, a computable theory of the procedure that it uses. We need a theory of the underlying neurophysiology (the 'hardware' of the nerve cells in which the procedure is embodied). Investigations that are restricted to only one of these levels are unlikely to yield a correct explanation.7

At this stage of development, a theory of the underlying neurophysiology is beyond the scope of this work. Instead, I will focus first on an explanation of how the system carries out the computation (which will admittedly be intermingled with what is being computed) and then focus on the question of what is being computed (in my terminology this question amounts to why things are funny). Using Marr's distinctions as a guide, we can see the importance of trying to isolate these separate levels of explanation in any good theory of a cognitive process.

The theory proposed in this treatise attempts to explain how humorous things, particularly witty sayings and funny one-liners, are computed. The theory does not attempt to explicitly define humor, and in fact refutes attempts to do so. Instead, I have proposed a rudimentary taxonomy of various types of jokes (classified according to their structure, and not their content) with an accompanying explanation of the relationships between the classes. The underlying idea is that once a humorous idea has been found (a problem for the "what/why" level of explanation), it still must be cast into a linguistic form. I have found a great deal of regularity, resembling a division into natural classes, in which jokes expressing fundamentally different content are told in a structurally equivalent manner. In a sense, these jokes belonging to the same class are essentially the same joke, and it is this generality that my theory attempts to capture.

Perhaps some comedians actually develop their jokes first, and then recast them in the appropriate structural form. This possibility is suggested by the corpus of one-liners I have gathered, as the comedians represented tend to display preferences for one family or another (see Woody Allen, Stephen Wright, and Groucho Marx). This component of the theory advances a hypothesis concerning "how" a joke is computed (created and/or understood).

The second component of this theory is concerned with answering the question of "what" is computed. Since, in the past, the bulk of the theories of humor have been occupied with this question, I have not gone far beyond their work, as most of it is valid in some contexts. However, I have attempted to go one step beyond this question , in an effort to place these theories in perspective, by asking "but why are those things funny?" This question has led me to develop the theory that humor is an emotion, and subject to many of the same constraints and concerns as other emotions. Of course, with a subject matter as vast as humor, there is much to say that I have left out. At best, I have simply provided a brief sketch of a fruitful direction in which to continue our studies of humor and creativity.

Before we dive into this theory, it is worthwhile review the major historical theories, since most instances of humor can be understood among them, although the levels of explanation are somewhat muddled.

3. Humorous History

"When a thing is funny, search it carefully for a hidden truth."

—George Bernard Shaw

How and why is something funny? The various approaches to these questions have focused on many different aspects of humor. Some theories emphasize the semantic content of the joke, while others rely on its syntactical form. In practice, these two elements are usually combined to produce the humorous effect, and it is difficult to isolate these components. Many of these theories are complementary, as a psychoanalytic or social theory of humor may operate in tandem with a cognitive theory. A single joke may be humorous for a multitude of reasons, and it might be too much to expect that a single theory of humor might account for all of the levels that a joke simultaneously engages.

The majority of humor theories fall into three broad classes: (1) social-behavioral, usually associated with derision and disparagement; (2) psychoanalytical, usually associated with suppression and repression; and (3) cognitive-perceptual, usually associated with incongruity.

Social-behavioral

And if you take the state of our minds when we see a comedy, do you realize that we have a mixture of pleasure and pain?8

The earliest known theory of humor is attributed to Plato, who observed that comedy in his time revolved around the humiliation of others. Laughing at the misfortune of others or at their expense is still prevalent in the humor of today, and these types of jokes fall into the category of derision or superiority humor. "Derision theory is based on the premise that we laugh down at others. Its basic drive is to humiliate, to subjugate, to disparage. . . . Even when the punch line is not disparaging, any joke which in its telling has negative connotations, directly or indirectly, is malicious and destructive."9 Supporting the completeness of this theory, W.C. Fields claimed that he "never saw anything funny that wasn't terrible. If it causes pain, it's funny; if it doesn't, it isn't." However, instances of humor which do not employ superiority are abundant, and it is clear from the laughter that a simple pun can elicit that the derision/superiority theory of humor is drastically incomplete. Arthur Koestler has characterized humor where "cruelty and boastful self-assertion are much in evidence" as childlike and primitive, as this type of humor is typically appreciated earliest in development.10 Given the similarities between childhood development and mankind's development, it is not surprising to find an abundance of this type of humor in the early stages of human civilization.11

The derision theory of humor extends beyond ancient times, and many attribute the modern formulation of this theory to Thomas Hobbes who wrote that "The passion of laughter is nothing else but sudden glory arising from the sudden conception of some eminency in ourselves, by comparison with the infirmity of others, or with our own infirmity."12 Georg Hegel expressed the similar view that laughter is little more than "an expression of self satisfied shrewdness."13

The hostility/superiority/malice/aggression/derision theory of humor is very much alive in contemporary psychological research,14 and plays an important role in the analysis of a joke's content. However, clearly not all derisive remarks are funny, so that even the jokes which this theory "explains" may also involve complicated mechanisms which dictate the form that a successful joke takes. There are many ways to insult somebody, and not all of them are funny. We may need to look to another level of joke explanation to complete our comic filter, and learn what makes X funny, and Y serious.

Psychoanalytical

Derision theory focuses on the relationship between the speaker and the listener, which while important, is not the only factor influencing the reception of a joke. Psychoanalytical theories, and more generally release theories, comment on the feelings and the psychology of the listener only (in the case of joke production, sometimes the speaker also acts as the listener). "The basic principle of all such theories is that laughter provides relief for mental, nervous, and/or psychic energy and thus insures homeostasis after a struggle, tension, strain, etc. This relief can be studied physiologically, psychologically, philosophically, psychoanalytically, or more or less generally."15

Darwin observed that laughter is primarily an instinctual expression of joy and happiness, strongly akin to an emotion, which may sound obvious to some and leaves us with the question of what causes joy and happiness. This is where Sigmund Freud's theories become relevant, as Freud devoted tremendous energy to explaining the causes of mental pleasure and pain. In his work on humor Freud concluded:

The pleasure in jokes has seemed to us to arise from an economy in expenditure upon inhibition, the pleasure in the comic from an economy in expenditure upon ideation (upon cathexis) and the pleasure in humor from an economy in expenditure upon feeling. . . . For the euphoria which we endeavor to reach by these means is nothing other than the mood of a period of life in which we were accustomed to deal with in our psychical work in general with a small expenditure of energy—the mood of our childhood, when we were ignorant of the comic, when we were incapable of jokes and when we had no need of humor to make us feel happy in our life.16

According to Freud, the pleasure derived from humor stems from two sources: the economy of effort in the joke, and the playful regression to old childhood pleasures. Freud also noted the parallel between dreams and jokes, which both seemed to employ the same techniques. These techniques include condensation (the fusing of two concepts into a single one), displacement (the shifting of emphasis from the relevant to the irrelevant), application of the same material, and double meanings.

Freud subdivided the funny into the 'comic', 'wit', and 'humor'. All three are assumed to wreak a false economy in psychic expenditure, liberating energy that is then dissipated in the expression of amusement. "Wit" is alleged to release energy from the inhibition of sexual and aggressive impulses, "humor" to offer relief by diverting energy from unpleasant emotion, and the "comic" to save the effort of thought. This latter is described as a psychological hoaxer, threatening mental demands that then prove void. There is a conflict of effort and lethargy and the audience procrastinate immediately, reserving their mental energy for more serious business.17

Freud may have been prompted to take up the subject of jokes when Wilhelm Fliess, upon reading the draft of Freud's The Interpretation of Dreams, complained that "the dreams were too full of jokes."18 Like dreams, Freud believed that jokes have uncanny access to the unconscious (here I am referring to the Freudian unconscious) and have the power to reach in and reveal aspects of the participants repressed desires and latent anxieties. According to Freud, the Id will often stage attacks on the Superego through the medium of wit, and, for this reason Freudian slips (in the form of puns, inversions, or distortions) are psychoanalytically meaningful and not just funny accidents.

The transition from Darwin's theory to the various stages of Freud's theory illustrates an important principle in the study of humor. The theory must strive to explain humor as deeply as possible, without simply grouping all of the instances of humor under one heading. Darwin claimed that the source of all humor is pleasure, but then failed to give a satisfactory account of pleasure. Freud not only attempted such a definition, but also tried to show how the various mechanisms of humor satisfy this account. His theory provides a model for how to link the specific instances of humor with their underlying structure, although he certainly did not complete the task of bridging the gap between the theory and the data. The release theories do not necessarily contradict the superiority theories since some jokes may evoke pleasure through superiority, although most release theorists did not believe that this is the only way for something to be funny.

Cognitive-perceptual

"Comedy is, as I said, a mimēsis of people worse than are found in the world—worse in the particular sense of 'uglier', as the ridiculous is a species of ugliness; for what we find funny is a blunder that does no serious damage or an ugliness that does not imply pain, the funny face, for instance, being one that is ugly and distorted, but not with pain."19

Based on this remaining fragment of the fifth chapter of Aristotle's Poetics, scholars have attributed the original "frustrated expectation" theory to Aristotle. The idea that humor is founded on a disappointment or unrealized expectation is more fully elaborated by later thinkers; however, Aristotle's theory contains the seeds for many later explorations. He goes in a different direction than the derision theory and recognizes the type of humor based on "make believe" that has been put on or set up all in good fun. His theory of humor best applies to absurd, clown-like situations in which the audience's awareness of the fantasy allows it to find humor in typically morbid themes (such as death, murder, or violence). This brand of humor can be found in many situations ranging from a pie in the face to a poorly-made horror movie. The significant feature of this theory is that it focuses on the joke itself rather than on the speaker or hearer of the joke. Later incarnations of this theory broaden its scope to incongruity of any sort, but one cannot help but wonder what might be contained in the missing sections of Aristotle's theory of humor.

Immanuel Kant developed Aristotle's absurdity theory and postulated that "Laughter is an affectation arising from a strained expectation being suddenly reduced to nothing."20 Schopenhauer essentially shared this view, and explicitly endorsed an incongruity-based theory of humor: "The cause of laughter in every case is simply the sudden perception of the incongruity between the concept and the real objects which have been thought through in some relation, and the laugh itself is just the expression of this incongruity."21 Researchers dispute whether incongruity is sufficient, or whether a joke requires incongruity immediately followed by resolution, and we will return to this point later. It is important to note that incongruity-resolutions theories parallel Koestler's "bisociation" theory, which is expressed in terms of the two notions of 'matrix' and 'code':

A code is a system of rules of process or performance and a matrix is 'any ability, habit, or skill, any pattern of ordered behavior' governed by a code. In particular, a matrix of thought is, or can for variety's sake be described as, a 'frame of reference', an 'associative context', a 'type of logic', or 'a universe of discourse'. Behind every act of creation lies a binary association (bisociation) of matrices: in that which produces laughter they collide, in a new intellectual synthesis they fuse, and in an aesthetic experience they confront each other or are juxtaposed. These three degrees of experience form a continuum, and may indeed grow out of the very same matrices. Thus the exuberant, explosive, tension-relieving delight (Eureka!) and the long after-glow ('the oceanic feeling') excited by an intellectual synthesis have their counterparts in laughter and the sense of satisfaction at seeing a joke.22

Koestler's method for the creation of jokes produces jokes which are funny according to the incongruity theory of humor. Raskin's formulation of the necessary and sufficient conditions for a text to be funny is founded on incongruity, and we will soon explore this bold theory in depth.

Most theorists believe that none of these theories of humor is complete, but that they are not necessarily incompatible with one another. For example, Frank MacHovec has recently proposed a theory of humor which attempts to synthesize the features of all of these theories. He speaks of humor's dependence on the convergence of three "cluster-like forces": polarity (direct feeling tone), power (force or valence of the feeling tone), and process (mechanics, details of technique; how polarity and power are focused). This theory demonstrates that most of the various theories can be successfully integrated with one another without excluding or favoring one theory, but this may indicate nothing more than their vagueness. Where the theories conflict, it is possible that the two versions simply produce jokes of varying funniness. For example, many slapstick routines depend upon the running gag, and are funny in virtue of the repetition of superiority, but after a while, are not particularly incongruous with anybody's expectations. In cases such as this, the two theories would predict different reactions (one would say it is funny, and the other would not), unless we stretched our interpretation of incongruity and analyzed the joke in terms of people not expecting the joke to continue for as long as it does. The fact that the theories do conflict on certain jokes that people find funny indicates that none of these theories is complete, and if it is possible to weasel a fit (as we just attempted to do in order to apply the incongruity theory to repetition) it may be that the theory is so vague that it can cover anything. We should be on our guard against both of these possibilities when evaluating theories of any sort, not just ones pertaining to humor.

MacHovec has argued that the problem with the incongruity theory on its own is that it is too focused on the micro-mechanistic nuts and bolts of the joke, and sometimes misses the larger context in which a joke is placed. Raskin, on the other hand claims to have found a script-based semantic theory of humor which provides all of the requirements for a joke. It will be important to keep these two viewpoints in mind as we explore the possibility of a complete, unifying theory of humor.

4. We're Off to See the Wizard

There are currently many humorists circulating what they claim to be comprehensive theories. Some are slight variations of preexisting theories, while some are beefed up syntheses of them. Victor Raskin has make the bold assertion that he has formulated a set of necessary and sufficient conditions for a text to be funny. He claims that his "semantic theory of humor is compatible with all three approaches [social- behavioral, psychoanalytical, cognitive-perceptual] simply because it does not concern itself with why something is funny, which is the focus of psychological theories of humor. It addresses a different question, namely, "How does a text convey humor?"23 He presents his theory as a full-fledged scientific hypothesis, subject to Popper's falsifiability criterion, which states that scientific sentences are falsifiable and unscientific sentences are not.24 The very application of Popper's criterion to a theory of humor has humorous merits on its own, but these are neutral with regards to the confirmation of the theory. His main hypothesis consists of two conditions that are expressed in the theory laden language of semantic linguistics:

"A text can be characterized as a single-joke-carrying text if [and only if] both of
the[se] conditions are satisfied.

(1) The text is compatible, fully or in part, with two different scripts.

(2) The two scripts with which the text is compatible are opposite in a special sense
defined [below]." 25

Raskin's hypothesis is written in a sort of shorthand, since concepts such as 'script' and 'opposite in a special way' are explained elsewhere. In order to fully understand the nature of Raskin's definition we must follow the script and take a brief detour.

The World According to the Script

Scripts were introduced during the ancient days of artificial intelligence (around twenty-five years ago) to cope with the problem of a machine processing natural language. Roger Schank was the major proponent of scripts, which began as a model of knowledge representation and grew into a more general theory of memory and association. The original problem that Schank was confronted with was the occurrence of sentences and situations that were impossible to understand without some piece of background knowledge. For example, the exchange

Q: Do you want a piece of chocolate?

A: I just had an ice cream cone.

cannot be understood without some prior outside knowledge not contained in the two sentences. Clearly, the response to the questions is intended to be a negative one, but there is not a direct chain of inferences that entail this conclusion. What is needed in order for the questioner to understand the response is the knowledge that people only want to eat when they are not full. This intermediate piece of outside knowledge provides the questioner with the missing link in his chain of reasoning, and allows him to conclude that the intention of the response, or its equivalent meaning, "No thanks, I do not want a piece of chocolate." This little piece of information does not constitute a complete script, according to Schank's theory, but it does provide an accurate model of the function that they serve.

Scripts are really just prepackaged sequences of causal chains. Some causal chains are used so often that we do not spell out enough of their details for an understander to make the connections directly. Scripts are a kind of key to connecting events together that do not connect by their superficial features but rather by the remembrance of their having been connected before. . . Scripts are not data structures that are available in one piece in some part of memory. Rather, script application is a reconstructive process. We build pieces of scripts as we need them from our store of knowledge as we hear them.26

The classic prototype of a script is the first script that Schank implemented, the restaurant script. This script stores information that is crucial for drawing inferences about restaurant situations such as the normal sequence of ordering, eating and paying. A story or a text about a restaurant scene might mention that someone entered the restaurant and assume that the reader understands the normal course of events and their proper interpretation implicit in that scenario. The question "Waiter, could you bring another round of drinks?" will be interpreted as an imperative request to bring another round of drinks, based upon the information that the restaurant script provides.

Schank identified a deep problem in language comprehension, and early responses to scripts were very receptive. However, in time even Schank was forced to abandon the primary role of scripts in the face of mounting difficulties with the script paradigm. One major problem concerned the relative specificity of a script. Would a person have separate scripts specifying a visit to a podiatrist's office and the orthodontist's, or would they have a single script specifying a visit to a health care professional? "Such a script is beyond [Shank's] initial conception of what a script was, because it was not specific enough. We had always believed that scripts were rooted in actual experiences rather than in abstractions and generalizations from experiences."27

Part of the trouble with the insistence upon scripts being rooted in actual experiences is that in the limit, this strategy ends up postulating a separate script for every possible experience that a person might have28, resulting in a highly inefficient middle man, whose explanatory role has been reduced to zero. If everybody must recall an individual script for every situation, they may as well remember the actual details of the situation itself, instead of constructing the virtually infinite number of scripts that such an organization would entail. At the same time, it does seem as if an inordinate number of scripts might be necessary, as there could be no single restaurant script, since for example, at fast food restaurants you pay and then eat, at diners you pay at the register after you eat, and at more upscale restaurants the waiter collects the check from you at the table. These concerns eventually lead Schank to expand his original idea of scripts into a complex recursive hierarchy which he named MOPs (Memory Organizing Packets). Under this revised model, Shank retained the use of scripts, but embedded them within a larger abstract hierarchy. He maintained that "scripts are not data structures that are available in one piece in some part of memory. Rather, script application is a reconstructive process. We build pieces of scripts as we need them from our store of knowledge to help us interpret what we hear."29

The finer differences between scripts and MOPs does not concern us here, although it is significant to note that the original proponent of scripts acknowledged himself that the model had serious flaws and required a substantive make-over in order to survive. Raskin, writing in 1985, may not have had the opportunity to study some of the later criticisms of scripts, and he does not directly address their limitations in his book. He justifies their usage based on the fact that no other system gets the linguistic job done as effectively as scripts do, and he points to their effectiveness in analyzing jokes as proof that they are feasible. However, we must be cautious in evaluating Raskin's evaluation of scripts and determine who is actually doing the work in Raskin's theory—scripts or Raskin himself. In his analysis, Raskin does not restrict the usage of scripts to the ones that have been implemented by Schank (or anybody else). Sometimes I will use his shorthand and refer to possible scripts that have not actually been implemented, as actual scripts.

Now Back to Our Regularly Scheduled Program

Raskin heavily employs the notion of scripts in his theory of humor and mostly passes the buck to this system in his analysis of jokes. His conditions stipulate that for a text to be funny it must be compatible with two scripts that are opposed in a certain way. Having outlined a working theory of scripts we must now turn to Raskin's condition of opposition. Raskin postulates three basic types of opposition between scripts, corresponding to the "real" and the "unreal" situation expressed by the text: (1) "The first type clearly distinguishes between the actual situation in which the hero of the joke finds himself or, somewhat more generally, in which the joke is actually set, and a non-actual, non-existing situation which is not compatible with the actual setting of the joke." (2) "The second type introduces the normal, expected state of affairs and opposes it to the abnormal, unexpected state of affairs." (3) "The third type distinguishes between a possible, plausible situation and a fully or partially impossible or much less plausible situation."30

Raskin enumerates a short list of the most frequently occurring oppositions, and devotes whole chapters to their standard instantiation in the particular categories of sexual, ethnic, and political humor. Raskin blurs his definition of opposition, by allowing for implicit second scripts in more complicated jokes. He also confuses the issue by specifying three conditions which are not logically independent. The best way to explore Raskin's theory is by applying it to an example and evaluating its performance. For example, consider this simple "joke" which Raskin spends over ten pages analyzing:

"Is the doctor at home?" the patient asked in his bronchial whisper. "No," the doctor's young and pretty wife whispered in reply. "Come right in."31

Raskin's model of comprehension involves the clarification of every word in the text and the selection of the correct meaning. In this joke the words "doctor" "patient" and "bronchial" evoke and re-evoke the script of a patient visiting a physician (the DOCTOR script). The fact that the doctor's wife is "young" and "pretty" is irrelevant on this first reading of the joke, and only comes into play after the script switch is triggered by an incongruity. When the wife "whispers" her invitation, after it is clear that there is no reason for the patient to stay if he came to see the doctor (she did not say "He's on the way back." or "You can wait if you like.") the search for other compatible scripts immediately produces the alternative scripts LOVER (or ADULTERY). As soon as this alternative script is discovered, all the loose ends of the joke are tied up, and it suddenly is clear that the doctor's wife was whispering because she was up to no good, and why it was important that she be young and pretty.

According to Raskin, "the joke is created by a partial overlap of two opposed scripts, tentatively labeled DOCTOR and LOVER. The opposition between the real and the unreal situations evoked by the text belongs to the actual/non-actual type. The non-actual situation exists externally as opposed to being conjectured by the hero(es) of the joke. There is a certain distance between the opposed scripts—they are neither the negations of each other nor compatible conjunctions of one another. They joke contains a discontinuous contradiction trigger."32

It is not obvious that all of this technical jargon enlightens our understanding of humor. Raskin's ambitious project is haunted by a number of serious shortcomings. His theory is built on the shaky foundations of script theory, and there may be some problems which will percolate up and threaten the integrity of his semantic theory of humor. Furthermore, as we will discuss below, the very possibility of formulating a rigorous definition of humor, as opposed to a theory, may be doomed from the start. However, before we concern ourselves with these broader methodological issues, it is worthwhile to examine Raskin's theory on its own terms, and to test its robustness while temporarily granting Raskin the benefit of the doubt with regards to the broader issues just mentioned. In particular, before we attempt to determine if any conditions would suffice, we ought to give Raskin a fair chance, and confirm the limits of his hypothesis.

What we need to show in order to demonstrate that Raskin's definition of 'joke' is not satisfactory is either one (or both) of the following: (a) That it suffers from the sin of omission— some texts are jokes, but are not included by the conditions stipulated in Raskin's main hypothesis. (b) That it suffers from the sin of commission— some texts are not jokes, but are included by Raskin.

Are there any texts that are jokes, but are not included by Raskin's conditions? This question is actually very difficult to answer, as it depends upon the leeway that we grant to the notion of a script. One reading of Raskin's theory provides us with numerous examples of texts that are funny but not included by the conditions. For example, many jokes contain a single script (euphemisms33, witty turns of phrase34, and even some simple noises35), or two scripts that are not in opposition to one another (puns or clever sayings which simultaneously convey two parallel, but unopposed meanings36). However, scripts are a very slippery concept, and their vagueness may allow a theorist to employ them without having them actually do any real work for the theory. For example, in many of his analyses, Raskin seemed to be explaining each joke individually (like the FORBIDDEN SEX, LACK OF SAVIOR VIVRE, and ZOOPHYLIC TENDENCIES scripts), and on its own terms in a way that is far more specific than the mere invocation of generalized scripts.

On one reading, Raskin's theory might be vacuous enough that someone dedicated to it could easily finagle an analysis in accordance with the theory. For example, the deadpan liar is often considered very funny in many settings37 but based solely on the information contained in the utterance, it is only comprised of a single script. If we were feeling generous, we might explain that there is an implicit second script which pits the script of the real versus the unreal, the liar versus the truth. However, it is unclear how Raskin's conditions identify such implicit scripts, and he makes up for this deficiency by fudging the analysis to fit his theory by a seemingly mechanical procedure.

The trouble with a vacuous theory is that it is not very informative, and if it wraps around everything without really explaining anything, it is not really much of a theory. This is one of the reasons that researchers have begun to demand machine-based implementations of theories; to expose the vagaries and ambiguities inherent in many such systems. Raskin's theory certainly does correctly evaluate many statements that we consider funny, but we should not expect the theory in its current form to be complete enough that an automaton could be taught a sense of humor. Considering that Schank only succeeded in implementing about a dozen scripts, and he was never truly able to test his hypothesis on a full corpus of real world data, and it is unclear whether his theory would have passed the test of the limitless possibilities that exist outside of the world of toy models—an actual novel is more than a simple extrapolation of restaurant, doctor, and lover scripts. Unless we grant scripts imaginary powers that they do not possess, thereby passing the buck to a nonexistent receiver, the dream (or perhaps nightmare?) of delimiting the set of what is funny seems to be in jeopardy.

Are there any texts that are not jokes, but are included by Raskin's conditions? Aside from omitting statements that most consider funny, Raskin's theory of humor also seems to miscategorize many markedly unfunny ideas as funny. Consider some of the famous logical paradoxes such as Zeno's paradox, the Liar's paradox or Russell's paradox. They all contain two "scripts" opposed in the appropriate way (I'm telling a lie versus I'm telling the truth) and yet most (save perhaps a few perverse logicians) do not find them to be at all humorous. Many of the most serious discussions in the history of science and philosophy involve the attempt to resolve opposing scripts, such as the wave-particle duality or the mind-body problem, and yet while its important to have a sense of humor about such matters (enter Schrödinger's cat), few consider the subjects themselves to be a source of mirth.

Raskin claims that his theory can distinguish a joke from a non-joke, but it cannot predict how people will react to it. It seems strange that according to Raskin's scheme, a text might be considered a joke even if it is not funny. In a sense, Raskin's theory redefines the term "joke", and we are free to follow his lead as long as we are conscious of this move. Consider the fact that some identical statements are hysterical in some situations and grounds for excommunication in others. This observation does not devastate a theory of humor, since it merely suggests that the theory should build into its conditions a stipulation regarding the context of the joke. Humorists such as Neal Norrick have identified this condition as the stipulation that the listener must be in playful or humorous mode/frame for him to be receptive to potential jokes. Jerry Palmer has described the joke-telling process as a negotiation, a theme we will later develop when we compare humor to other phenomena. If humor is a complex negotiated interaction between the speaker (sometimes the mute ink splotches on a page) and the listener, then all that we expect from a theory is a specification of the nature of the context that is required for a funny statement to be received as funny. If we take this approach, we are not forced to redefine humor in a way that is uncorrelated to what people consider funny.

Raskin is not a lone maverick for thinking that incongruity is intimately connected to humor, and some have actually tried to quantify the relationship between the two, expressing the funniness of a joke as a function of the incongruity it expresses. A number of studies have also been designed in an attempt to empirically test the hypothesis that non- verbal humor is merely incongruity. G. Nerhardt conducted a series of experiments in which the subjects were asked to lift weights and rate their heaviness.38 The weights were incremented every trial, establishing an expectation for their heaviness. On the last trial the weight was either sharply reduced or increased, and this last incongruous weight evoked laughter (the probability of laughter increased "as a linear function of the discrepancy form expectation").

Nerhardt hoped to show that incongruity was at least a sufficient, if not necessary, condition for something to be funny. Unfortunately, the control group of subjects whose final trial weights were in accordance with the pattern, sometimes laughed at their final trial. Nerhardt felt that this indicated that laughter has multiple meanings and functions, and argued that laughter without amusement or a stimulus of incongruity might reflect friendliness or unease. On the other hand, we might think that there was something inherently humorous (although not necessarily absurd) about his experimental setup which caused the reaction that he measured. In either case, this experiment illustrates how empirical studies of reactions to humor have proven to be very difficult. Not only is it hard to interpret the subjects' reactions, but it is difficult to design experiments since concepts such as incongruity and semantic distance are hard to quantify and there is no good standard by which to measure them.

5. What's in a Definition?

What type of humor criterion are we after? Some researchers, such as Raskin, fantasize about a set of conditions that specify exactly when a given sentence is funny. But, we must bear in mind that rigorous analyses that demand necessary and sufficient conditions often fail to withstand the onslaught of clever philosophers with witty counter-examples. For some concepts, it is fruitless to expect this type of definition, although much can be learned by attempting to find one. What we really need is not a definition, but a theory of humor that can develop and grow with our understanding, as well as guide us in the direction of future research.

The Precedence for the Indefinability of Concepts.

Some philosophers acknowledge that certain concepts are indefinable due to their atomic nature. For example, G.E. Moore presented a famous argument for the indefinability of "good" based on the fact that for any possible definition proposed, it can meaningfully be asked whether or not that definition is good39. Formally this can be expressed as follows:

If "x is 'y' iff x is D" is a definition of 'y', then 'y' and D are synonyms
(intersubstitutable).

If 'y' and D are synonyms, the question (Q) "Granted y is D, is x 'y'?" is a trivial,

self-answering one.

If Q is never (except trivially) meaningless, then there must not exist a D that is

synonymous with 'y'.

Moore made this argument for [y = good], and concluded that aside from a few uninformative examples such as "x is 'good' iff x has value." This question (Q) is always meaningful, so, there are no definitions of good. It is important to note that good is not the only concept that could be substituted for y, and that we can apply his argument to the case where [y = funny].

Moore asserts that apart from trivialities such as 'x is good iff x has value' and 'x is good iff x ought to exist for its own sake' there are no definitions of x that make (Q) vacuous. One problem with this argument is that Moore provides no procedure for determining if there exists some non-trivial D such that (Q) is self-answering. Of course, Moore can insist that his argument shifts the burden of proof to the proponents of rigorous definitions for 'y', who must now produce such a D to defeat Moore's claim, however, it is still possible that such a D does exist, it's just that nobody has ever thought of it. In other words, the Open Question argument describes one of the properties of an atomic concept, namely that it is always meaningful to ask "Is x 'y'?" when y is atomic. However, Moore's argument does not provide any procedure, aside from intuition, which determines whether or not such a y exists. In this respect the argument is fundamentally inconclusive—it can tell you with certainty that a concept is definable, but it will always leave a lingering doubt as to a concept's indefinability.

The applicability of this argument to the concept of humor is not as clear cut as Moore's argument against the definability of good, since in the case of [y = good] Moore expresses a claim which seems correct, and with which many philosophers agree. However, it remains to be seen whether we can find a non-trivial D such that the question "Granted x is D, is x funny?" is always self-answering. The existence of such a D would provide us with a definition of funny that would specify the precise conditions under which x is funny. As Moore's argument demonstrates, it is not at all obvious that such a definition needs to exist for all concepts. The question is whether 'funny' is the type of concept that is indefinable, or if it can actually be specified by some synonymous criterion.

If there were no D that provided us with a Moorian definition of humor, it would not be time to wave the white flag. Our inability to define a term in Moore's sense of definability should not threaten our conviction of the power, significance, and meaning of that term. We would be hard pressed to formulate a Moorian definition of many concepts, such as identity, game, heap, or lamppost, and yet most of us have little difficulty using them meaningfully in a sentence. Moore's standards of definition may be too stringent for all but a few concepts, especially as a scientific theory strives to capture a working definition of a phenomena that may change over time.

A Prototypical Theory

An important fact which these studies and examples teaches us is the futility of searching for the absolute, necessary and sufficient conditions which define the concept 'funny'. In his analysis of the concept of games in the Philosophical Investigations, Ludwig Wittgenstein noted that there is no fixed concept of a game itself. Different games (board games, card games, athletic games, for example) have no one thing in common, other than being human activities which are "played" by rules. The resemblance among the games is like that shown among members of a family, each unique yet somehow similar to one another. Under this schema, the determination of a new judgment is based upon the comparison between known instances, and paradigm instances of the concept provide the axes that span the meaning of the concept without rigidly defining it.

This procedure is a common cognitive technique that is employed in many different tasks and may play a central role in determining the funniness of a particular situation. Something may be judged funny if it is similar in a crucial way to another previously known funny instance. Perhaps we were chasing our own tails in searching for a single unifying criterion that all humor must satisfy, and we ought to consider a disjoint definition whose members bear a familial resemblance to one another, but cannot be boxed and shipped as many humorists have hoped

Peter Strawson suggests this approach in his analysis of personal responsibility, and it is interesting to retrace his argument, bearing in mind its potential application to humor. Strawson has argued that

there is no independent notion of responsibility that explains the property of the reactive attitudes. The explanatory priority is the other way around: It is not that we hold people responsible because they are responsible; rather, the idea (our idea) that we are responsible is to be understood by the practice, which itself is not a matter of holding some propositions to be true, but of expressing our concerns and demands about our treatment of one another.40

By defining responsibility in terms of people's reactive attitudes, Strawson sets us up an account of responsibility that resists rigorous analysis. Following Strawson's lead, we might find that we can make significant headway by defining funniness in terms of what people find funny.

It has been shown experimentally that some areas of knowledge representation probably operate according to the prototype model.41 That is, when asked to identify whether an object B is a bird, we do not employ a propositional conditional that is satisfied just when B is a bird. Rather, we compare B to an prototypical bird (i.e. a canary) and determine the similarity of B to the prototype. This feature of human cognition is easy to detect through introspection in the case of moral evaluations. We often do not first know what our reactive attitude "should" be, and although an attitude is supposed to be an instinctive response, even our intuitions are at a loss in some cases. In these instances we tend to compare the case with other cases whose evaluations we are sure of by extracting the relevant features and determining if the uncertain case fits the mold (much like identifying object B). However, in order for this strategy to be effective we must have clear cut, prototypical examples with which we can preform this comparison. In the next chapter we will continue to examine this avenue of analysis in greater depth to see if it can be applied to the analysis of humor.

6. A Positive Alternative

If humor is indeed an emotion, an idea we will examine in later chapters, there is a precedence for the fact that, like Strawsonian morals, we may not be able to define it. The Polish linguist Anna Wierzbicka encountered this problem in trying to define the basic emotion 'sadness'.42 She conceded that the structure of feelings prevents them from being expressed in words since basic feelings are signals which have no symbolic structure, and consequently do not correspond to any analytical concepts. Of course, we would like to be able to say more about a concept other than that it is ineffable and cannot be expressed in words. Following Wittgenstein's lead, there may be merit in examining the disjoint prototypical phenomena that comprise the concept of 'funny' in the hopes that we may discover family resemblances between various members of this set, which in turn may lend themselves more readily to an analysis.

There is good reason to think that humor is a disjoint phenomenon of this type. Aside from the exceptionally large variety of things which different cultures find humorous,43 individual senses of humor vary from person to person, and even within the same person over his lifetime. People learn to appreciate new forms of humor, either through association with forms that they already consider funny, or eventually by actually creating a new category of things which they consider funny. For example, there is a point in the development of children where they begin to appreciate sarcastic comments (although some people never find them funny), whereas previously they simply took them at face value. Not only do our senses of humor become increasingly refined over our lifetimes, but they also develop in other ways, as we no longer find funny (or at least we don't admit it) jokes we consider childish or primitive as we are busy cultivating new modes of comedic expression.

Many of these modes of expression are highly idiosyncratic, as Bill Cosby, Robin Williams, and Jim Carey can all attest. There are certain bits that these comedians perform that are only funny because they said it, in a way that only they could. This phenomenon carries over into the domain of written humor, as the humor of many jokes relies upon their author. For example, take a saying attributed to Herotodus (its authenticity is not an issue here):

Very few things happen at the right time, and the rest do not happen at all. The
conscientious historian will correct these defects.

A significant portion of the humor in this statement lies in the recognition that it was written by a man who is considered the father of history. Had a revisionist historian, a malicious dictator, or even an average human uttered these same words, much of the joke's punch would be lost. 44 Again, we could try to specify within our humor identifier/generator the fact that X is only funny if Y, or someone like Y, says it, but at a certain point it seems that we must acknowledge the disjointed nature of humor. We are left wondering whether there is in fact a broad umbrella under which these disparate forms of humor all take shelter.

Given the demonstrated failure of many humorists to comprehensively specify the conditions for all humor, it might be fruitful to shift gears, constructing a theory from the bottom up. To carrying out this strategy, I have gathered about a hundred one-liners and created a taxonomy, based primarily on technique as opposed to content. As Freud pointed out, "It must be repeated in advance that the technical species of the joke—whether it is a verbal or a conceptual joke—bears no relation to [its] purpose."45 I chose to work primarily with one-liners since they often seem to encapsulate the longer jokes that employ their main idea as a punchline. Also, they form a relatively well defined set of jokes that would be far easier to parse or generate than a full length story joke. One-liners are a form of concentrated humor, and although they are not usually quite as funny as elaborated versions, most humorists have found that it is easier to work with jokes on the unfunny side of the spectrum since they facilitate the isolation of the relevant factors at work.

7. Meet the Family

In many instances the various theories we have considered are remarkably accurate in explaining different aspects of a joke's appeal. Their drawbacks center mainly around claims to strictly delimit the domain of what is funny, using their theory as a guideline. We have demonstrated that 'funny' might not be the kind of concept that can be defined in terms of necessary and sufficient conditions, and we have also suggested an alternative approach for developing a working theory of humor—one that tries to define what we don't know in terms of what we do. We have seen that the trouble with theories of humor is that they are either expressed in a such a vague manner that they becomes vacuous, or in such a restrictive manner that it ceases to fully describe the phenomenon. We need to be cautious so that we do not fall into a similar trap.

In light of our hope to burrow into the mechanics of the generation/recognition of humor, it makes sense to focus on the cognitive-perceptual theories of humor, primarily equated with incongruity theories. We will not ignore the psychoanalytic and social factors that also operate in most jokes, but our families of jokes will be clustered around ways of expressing incongruity. The choice to organize our data primarily around incongruity reflects the applicability of this mode of analysis to the problem which we are trying to solve. Incongruity is often created at the "nuts and bolts" level of the joke, dictated mostly by syntax, although still subject to semantic constraints. Other forms of humor are very often expressed in an incongruous form (in fact, the other theories of humor often form the basis for the semantic constraints), as the meat of the joke must be held together by slices of bread. We will never understand the essence of the sandwich until we have a theory of the relationship between its contents and the structure that keeps it from falling all over our laps. Under a loose reading of 'incongruity', we will be able to accommodate all the categories we encounter, and even generate new ones not found in our limited corpus.

Although the form and the content of a joke are intimately related, it is still possible to tease apart these components of a joke and categorize them according to either scheme. Many humorists choose to classify jokes in terms of their content, i.e. sexual, political, or ethnic. The decision to classify this corpus of jokes according to their structural form was based upon a number of factors.

First, it was observed that jokes with wildly varying content are often expressed using a similar (or even identical) structural form. This suggests that the mechanism for generating/recognizing a joke may involve a knowledge of these families of techniques, and a possible disjoint definition of humor begins to take shape.

For jokes that belong to the same family, there is also a strong sense that all the members of that family convey humor for many of the same reasons, and from a certain perspective they are all the same joke. While it is silly to deny the semantic contribution to the funniness of the joke, the syntax of a natural language constrains the joke in particular ways that become apparent when trying to generate a taxonomy of these jokes based upon the technique, and not the subject matter.

I predict that the categories I have created are evident enough that a group of subjects given a set of one-liners and instructed to group them according the principles I have outlined, would place them in very similar categories to the ones that I have found. I have not carried out this experiment formally, due to lack of resources, but I am confident that a meaningful, regular pattern, similar to the one I have found, would emerge from such a trial.

This confidence stems from the fact that even if we cannot specify precisely what it means for a sentence to be incongruous, there are only so many ways to do so in a natural language. The taxonomic tree that I have postulated based on this principle is not complete, partially due to a relatively small corpus, and it may be incorrect in some of its details. However, I believe that the general direction of future research suggested by this tree is valid, and should lead to productive results.

The difficulty in getting this kind of taxonomy correct should be evident from the non-dichotomous structure of the tree. Gathering a representative collection of one-liners is not an easy task, despite the abundance of joke books. Reams of material (mostly mediocre) can also be heard daily, but whenever the tree is thought to be complete, a new family inevitably seems to pop out of nowhere. Furthermore, until an attempt is made to exhaustively describe the family, it is hard to determine if enough divisions have been made, or if the family is still too large to define. Although some a priori divisions can be appealed to (i.e. jokes can either involve idiosyncratic knowledge or not) it is hard to tell when these divisions are necessary as opposed to arbitrary. Finally, many jokes do not fit cleanly into a single category, and sometimes they are categorized somewhat arbitrarily to demonstrate the existence of jokes in that family. Even if a case could be made for their inclusion in other families, there is nothing wrong with a joke belonging to multiple families—it is just more complicated than an non-compound joke. The following tree ought to be viewed as a preliminary sketch, and not a definitive (pun intended) solution to the task of dividing the problem space into its natural components. (see Figure 1).

The purpose of breaking down the families of one-liners is to show that there is a great deal of regularity, and in some cases the beginnings of a well defined grammar, within the various groups of jokes. By disassembling the problem of humor into small enough parts, it may be possible to specify very accurately the conditions that members in that family must satisfy.

In the following sections, I will describe the relationships between the nodes of the tree as well as describe the families (otherwise known as the terminal nodes or leaves) that the tree generates. I have also selected about half-a-dozen families to analyze in depth, and have attempted to specify the precise conditions which entail membership in these families.

I have only fully analyzed a limited number of leaves since the task of specifying the precise conditions proved to be monumental, and requires a great deal of painstaking revision. The leaves that I have analyzed, in addition to describing, should demonstrate that this project is feasible, and it could be completed by devoting further time and effort. Getting right the conditions for membership in a family is a tricky job that would require a much larger corpus than the one that I have gathered, and might be facilitated by actually implementing the conditions in the form of a computer program.

The ability to construct a robust specification for even a single one of these families suggests that this approach might prove important at some point in the future. The theory in its current form provides the outline for further research on humor, which in turn may be used to help construct a more comprehensive theory of creativity. Most of the families are simply described along with a rough sketch of what the generating algorithm would look like. A few are treated more rigorously and include a more thorough (although not complete) analysis. By analyzing a few families thoroughly, I simply intend to prove the feasibility and usefulness of this theory, not its completeness.

How can somebody be incongruous?

This question motivates the organization of this theory of humor, and serves to generate the rest of the taxonomy. Again, choosing this question as a starting point does not commit us exclusively to an incongruity theory, it simply dictates the manner in which we will categorize the jokes.

Once we have agreed upon this starting point, a natural division to construct is between jokes which rely upon a specific piece of outside knowledge and those jokes which contain within them all of the information necessary for their comprehension. Of course, to appreciate any joke a great deal of outside knowledge is required, including a working knowledge of the language(s) of the joke and a basic common-sense knowledge of the human condition.46 This distinction is intended to differentiate between those jokes which depend upon a single piece of idiosyncratic knowledge, such as a particular saying or a turn of phrase, and those jokes in which a general listener would be expected to understand.

There are some families which require knowledge that is borderline according to this division, but as we are trying to escape from the world of hard and fast boundaries, we will bracket this problem. We should also bear in mind that the goal of this taxonomy is to produce healthy families, which correspond to the leaf nodes on the tree. In many respects the internal structure of the tree is secondary to the classes that it generates. Ideally, the tree will not only explain classes found in the corpus, but will predict new families as well. For now, if there are some families whose placement in the tree is uncertain, we need not be overly concerned, as long as they fit in somewhere. It is also important to remember than many jokes belong to more than one family, and multi-family jokes were often categorized to illustrate the validity of a particular family.

Shattered Expectations

As is evident in Figure 1, significant portions of both sides of the tree are composed of sub-families whose basic strategy revolves around the violation of the listener's expectations (Shattered Expectations). This division contrasts with the general heading of incongruity since incongruity can be produced even when the listener has no specific expectations (see Biassociations), or precisely when his expectations are fulfilled (see Repetitions). A generous reading of Raskin would include most of these jokes, if we allow for a very loose understanding of the term "script."

Since there are many different types of expectations that people can have, there is more than one way to violate them. I have broken down the types of expectations that people can have into two broad classes: Linguistic and Conceptual. Linguistic expectations can involve expectations about the particular Word Choice, evident, for example, in puns which would not work the same way if a different word were substituted for the pun. Linguistic expectation can also involve expectations concerning the Overall Structure of the sentence, such as expecting certain sentences to present you with a adjective and its antonym, an expectation whose violation can produce humor, and gives rise to a family ((False) Antonyms) which we will discuss shortly. In addition to linguistic expectations, people can also harbor conceptual expectations concerning the meaning of a sentence, which can usually be violated in way that does not depend upon a particular formulation (although they sometimes exploit the multiple senses of a single word as in a Fork in the Garden Path).

This division highlights an interesting feature of jokes involving their translatabiliy into a foreign language. In many instances where a joke depends upon a single word or a linguistic norm, it will be nearly impossible to translate the joke into a foreign tongue unless the target language contains a word with very similar meanings. On the other hand, jokes that rely upon conceptual expectations can often be translated with some success since the exact wording of the joke is not as important as its meaning. The difficulty in translating jokes can be seen in the translation of Freud's Jokes and the Unconscious, in which it is obvious that the translator had to struggle with some jokes more than others (he actually gives up on some and offers the German to illustrate Freud's point). Both types of jokes are also subject to "translation" over time, as most humor, conceptual or linguistic, is not universal and what is funny here and now may not be funny somewhere else or later. We will take up this theme further in Part II.

(False) Antonyms

A fairly simple, but common form of one-liners is what I have termed (False) Antonyms:

Life is divided into the horrible and the miserable.—Woody Allen

You've gotta take the bitter with the sour.—Samuel Goldwyn

These jokes play off of the opposition of the antonym script (the typical sentence in which an opposition is set up between an adjective and its opposite) and the actual joke in which the second adjective is a synonym of (or in the third case, identical with) the first. Of course we must place some restriction on the content of the joke, namely the relationship between what is being described and its description, since it would certainly not be funny for Allen to say that *"Cheese is divided between the horrible and the miserable" or *"Life is divided between pleasure and ecstasy." However, it is not difficult to imagine many other subjects joked about successfully in this manner. For example, the frame "NOUN is divided into ADJ and ADJ" might readily be filled in appropriately for the topics of sex, friendship, eating, relatives, etc. and it becomes easier to imagine writing a computer program that could generate jokes of this form. However, it is important to note that aside from the knowledge required to understand natural language, this family of humor relies upon the fact that listeners have already been trained to expect certain frames, such as the "X is divided between Y and the-opposite-of-Y", and also have the life experience to recognize the relevant stereotypes being exaggerated. For this reason, it is included among the members of jokes which shatter linguistic expectations concerning the overall structure of the joke. It could be argued that knowledge of the overall structure of the sentence (namely, that sentences of this sort usually describe the noun in terms of an adjective and its antonym) is basic to any native speaker of English, and this family should be placed on the other side of the tree. However, since it is easy to conceive of an English speaker who is not aware of this convention, I have conceived of this family as one which relies upon a specific piece of outside knowledge.

The restriction that we must place on the topics which can be joked about in this manner will not be one based solely on the syntax of the joke. Nouns may not be chosen randomly, as sentences such as *"Cheese can be divided into soft and mushy." attest. Successful contenders for this style of joke will most typically come from emotionally charged domains with which most people have some experience and/or stereotypes. The noun 'cheese' might be joked about in terms of its relation to weight loss and the seductive taste of fat, but not easily in terms of its texture or consistently. Borrowing an example from the Smart Ass family " Deep fried cheese—a cardiovascular dream come true." we find that a seeming random noun such as cheese can be joked about, as long as an emotionally charged relation can be established between it and the audience. A detailed discussion of what makes a subject emotionally charged will follow in Part II, but for now we can simply understand the term as anything that people care about.

This restriction also applies to the selection of adjectives, as not all sets of synonymous adjectives will be funny. Thus, the choice of the noun might be carried out randomly as long as the noun can be related to an emotionally charged description that a even-minded person could view from two perspectives, but a cynic would view from just one. *"Life is divided between pleasure and ecstasy." is not funny because it is too cheerful and does not address the day to day misery that many people experience but are forced to repress. This reasoning should allow one to construct jokes fitting this template for virtually any appropriate noun, provided that a stereotypically cynical relation can be found to describe it. "Friendship is divided between arguing and bickering" or "Relatives are divided between the obnoxious and overbearing" were both constructed according to these guidelines. While these jokes are not hysterical, they are humorous for many of the same reasons that the examples are, since in a significant sense, they are all the same joke.

The class of (False) Antonyms is closely related in form to the true antonym (hence the parentheses) where the two antonyms completely describe all of the possible states of affairs:

In love there are two evils: war and peace.—Horace

A "Bay Area Bisexual" told me that I didn't quite coincide with either of her desires.

—Woody Allen

Horace does not come straight out and say that love is evil, however by equating love's evil with an exhaustive list of the possible states that two lovers could be in, he effectively (and more humorously) manages to make an equivalent claim. We realize that Allen employs this same technique, once we figure out that humans only come in two sexes, and bisexual's interests exhaust all the gender possibilities. While the content differs substantially, in many ways these two jokes are the same joke. Again, this technique will not always produce a funny statement, however, it is a time tested template for many effective variations.

The "true antonym" can be constructed for the same classes of subjects as the "false antonym." Horace might have constructed his joke as "Love is divided between the painful and the heart-breaking" which expresses essentially the same sentiment as the form he chose. The similarity between these two templates allows for easy conversions between one form and another, and both lend themselves to joking about subjects restricted in the same way.

Surprise Instance

Another family of one-liners, which all partake of fundamentally related techniques is the class of Surprise Instance. This time the family falls under the Conceptual branch of Shattered Expectations, and earns its laughs by inserting an inapplicable or paradoxical instance into a well known idiom or turn of phrase.

I phoned my Dad to tell him I had stopped smoking. He called me a quitter.

—Stephen Pearl

Quitting smoking does fit the literal script for being a quitter, but while being a quitter is generally considered a negative quality, quitting smoking is a positive accomplishment, and the application of an instance which literally fits the script but does not match its connotations characterizes members of the "surprise instance" family. In a way, this family does pit two scripts against one another, as the general script is matched against one of its alleged members, which proves to be an exception to the rule. But exceptions to the rule are not always funny (when learning a language they are notoriously unfunny) so we need to be more specific in our analysis of this form. A few more examples will help us generalize more accurately47:

I bought some batteries, but they weren't included.—Steven Wright

Here Wright is playing-off of the fact that many advertisements for products contain the disclaimer "batteries not included" and he capitalizes on the fact that this tag will momentarily sound normal. The sentence is syntactically well formed, and even makes sense on a first semantic pass, until we realize the absurdity of somebody buying (or selling) batteries where the batteries are not included. Similarly,

There will be a rain dance Friday night, weather permitting.—George Carlin

exploits the same strategy of using a perfectly normal turn of phrase ('weather permitting'), but tacking it on to the end of a clause which is totally incongruous to it. If it rains on Friday night, then there will be no need to reschedule the rain dance, since the purpose of the rain dance is to create a situation in which the weather does not permit outdoor gatherings (so to speak).

Both of these examples demonstrate classic examples of the Surprise Instance family of jokes. To construct such a joke, first find a common turn of phrase that can easily be appended to many sayings. Then attach it to a sentence which renders the use of that idiom nonsensical based upon the content of that particular sentence. For example, take the common appendage "God willing." A joke might be constructed by formulating a sentence along the lines "In the coming century most people will become atheists, God willing." By combining the common idiom with a sentence which either negates or makes it logically incompatible, new instances of family may be generated.

Sometimes this exercise will produce a hybrid joke, which exploits the principles of more than one family. For example,

Sometimes too much to drink is barely enough.—Mark Twain

fits into this family since Twain seems to have described a surprise instance where having too much of something is not actually enough. However, we can also analyze this joke based on the idea that the phrase "too much to drink" has two senses. First, too much to drink can mean 'more than a person can handle drinking'; second, too much to drink can mean 'a person is drunk'. In both cases it is possible for the subject to feel as if he has not yet had enough to drink, although Twain appears to be playing with the second sense of "too much." As we shall see soon, there is another family of jokes which specifically exploits this type of ambiguity, although this particular joke is more akin to Surprise Instances than Forks in the Garden Path.

(In)Famous Last Words

Sibling to the Surprise Instances is a family of one-liners that is parasitic upon well known sayings, which are reworded and subverted to the comedian's purpose. Most of these jokes will pass clear over the heads of all who are unfamiliar with the sayings, although some are funny enough to stand alone (although they stand taller in reference to their original incarnation). An easy algorithm which generates this sort of humor (instant incongruity combined with sexual innuendo) is a game that can be played at the end of any Chinese dinner. Simply open your fortune cookie, read the fortune aloud, and tack on the words "in bed" to the end of the sentence.48

The following examples of (In)Famous Last Words are constructed by negating a single element of the original in order to completely reverse its meaning, but still sound enough like the original to momentarily fool the listener.

I'm not young enough to know everything.—Oscar Wilde

(I'm not old enough to know everything.)

Never put off until tomorrow what you can do the day after tomorrow.—Mark Twain

(Never put off until tomorrow what you can do today.)

Of course, the reversal of meaning is not the only transformation that can be carried out on a saying, as it is also popular to turn the saying into nonsense or a truism:

If the phone doesn't ring it's me.— Jimmy Buffet

(If the phone rings its me.)

You are where you eat.—Unknown

(You are what you eat.)

Sayings can be converted to express popular cynical sentiments, as we saw in the popular "(False) Antonym" category:

The shortest distance between two points is usually under repair.—Unknown

(The shortest distance between two points is a straight line.)

Or, even distort the original metaphorical intention of the saying, by reading it literally (we will also encounter this technique in the family of Definitions).

Curiosity killed the cat, but for a while I was suspect.—Steven Wright

(Curiosity killed the cat.)

There are many funny variations that can result when playing with well know sayings, but the reversal of its intention by the negation of a single phrase is the easiest and the most popular. However, the joke need not end with the a simple negation, as these examples show. Strategies employed in the formation of other families are also applicable here, although no general algorithm may be specified due to the variety of potential inputs (virtually any saying could become well known and ripe for ridicule).

A Fork in the Garden Path

Jumping over to the mirror branch of Shattered Expectations on the All Necessary Information Contained in the Joke side (the right half) of the tree, the next family we will visit is A Fork in the Garden Path. These jokes typically exploit the semantic ambiguity inherent in natural language by suggesting a certain sense for a verb, and then revealing that an altogether different sense is consistent and was actually intended by the comedian. For example,

I take my children everywhere, but they always find their way back home.—Robert Orben

This one-liner sets up the listener by suggesting that Orben takes, in the sense of conducts or guides49, his children with him where ever he goes, when in fact, Orben then disambiguates this seemingly clear sentence to mean that he brings his children places, and then leaves them there50. The joke would not be as funny if initially there were no ambiguity, *"I abandon my children everywhere, but they always find their way home." Furthermore, it is not sufficient to disambiguate a word from any sense to any other of its senses. So, for example, *"I take my children everywhere, but my arms keep getting tired."51 is not as funny as the original either. The humor is maximized when the hidden sense reveals a reading that is culturally shocking or violates common sense, and yet is somehow innocent, since its meaning was accessible to the audience from the start.

It is common to find comedians creating ambiguous sentences using verbs that have many senses such as "take" "give" and "get" since it is easier to invent sentences with multiple interpretations.

My doctor gave me two weeks to live. I hope they're in August.—Ronnie Shakes52

I got food poisoning today. I don't know when I'll use it.—Steven Wright.53

Both of these one-liners exhibit the standard "Fork in the Garden Path" strategy by exploiting the implicit assumptions that we make when disambiguating common idioms, and substituting radically different, but wholly consistent, interpretations for them.

While this family of jokes does rely upon basic outside knowledge concerning common ways of disambiguating words, this type of knowledge is not as specific as that required for understanding the jokes we have examined up until now. The outside knowledge required to understand Forks in the Garden Path is so basic that without it, it would be impossible to understand the sentences, even without appreciating the humor in them. The humor in jokes we have seen earlier rely upon specific bits of outside knowledge, such as a convention or a saying. For this reason, I have created a branching in the taxonomy that reflects this distinction, since most jokes in this category ought to be accessible to anybody who speaks English.

Generating jokes of this type should not be too difficult, considering that it is a very prevalent form of joking. 54 A computer program could simply start with an activity whose verb phrase is ambiguous, and construct a sentence that leaves the common interpretation intact, while explicitly revealing an alternative interpretation in the latter half of the joke. Not every sentence produced in such a manner will be funny, and the basic guidelines outlined in previous families, such as emotionally charged subject matter portraying stereotypical attitudes, will serve here as well. This family may even have more leeway than previous groups, since most logical absurdities and shockingly evil or criminal actions also function well as humor in this form. These alternative themes work here and not always elsewhere since an essential component of Fork in the Garden Path jokes is the idea that the audience goes along with the original proposal, and suddenly finds themselves with their pants down, endorsing an activity which they might have denounced previously. In short, this form is tremendously flexible, as it ranges from nonsense, along the lines of Marx's taking the plane to Chicago, to DeGeneris' harsh sentiment that we wouldn't really miss our elderly relatives if they disappeared. In between is the twisted psychosis of Wright, who fools us into becoming accomplices on his serial poisoning spree. Based on conversational evidence (ambiguities are frequent sources of conversational joking), it is difficult to imagine a fork of the proper form which is not nominally funny, but various constraints on the content would allow a program to produce humor according to a particular style, often funnier than a generic random ambiguity.

Could You Rephrase That?

Moving on to the linguistic branch of the Shattered Expectations node, another family which is accessible to anybody who is fluent in English is the class of jokes that relies upon internal restructuring of the sentence as it is being uttered.

Wise men talk because they have something to say. Fools talk because they have to say
something.—Plato

The difference between literature and journalism is that journalism is unreadable and
literature is not read.—Oscar Wilde

These one-liners are closely related to the classic pun (one word; two meanings), and derive a significant amount of humor from words which sound very similar, but mean very different things. The specific wording is crucial for these jokes since they rely upon the auditory association which results from a simple reordering of the words. It is as if the audience is baffled by the fact that a radically different meaning can be generated by such a small change in the syntax of the sentence. We might even call this class the family of syntax puns. Note, that both of these sentences also overlap with the family of "(false) antonyms" but that their humor is primarily a function of wordplay and syntactical inversion.

Sometimes the wordplay is implicit, as the following demonstrates:

Why is there so much month left at the end of the money?—Unknown

Here the reader almost automatically compares this sentence with the more standard construction *"Why is there so little money left at the end of the month?" recognizing and sharing the common sentiment of feeling broke and wondering where he spent all his money.

In general, this type of humor is also very prevalent in conversational joking, as many would-be-comedians earn a laugh by inverting or rearranging the words of their fellows in a way that preserves the grammaticalness of the sentence, but also inverts its meaning. As long as the inversion is still meaningful, the sentence ought to be nominally funny, although all of the restrictions outlined above apply equally to this form of humor as well. Conceivably, a computer program might process sentences, by inverting the structure of the sentence through trial and error until a new meaningful sentence is formed. If the meaning of the new sentence is related to the original in a particular way, i.e. opposite or conveying a more realist state of affairs, chances are it will be a funny way of expressing the thought.

Self-Referential

Another reliable method of eliciting laughter, and a sibling of Rephrase That, is the use of sentences which refer to themselves, or are instantiations of the state of affairs they describe.

There are two kinds of people, those who finish what they start, and so on.

—Robert Byrne

This is not a surefire method, as many self referential sentences are not humorous (i.e. *"This sentence no verb."). However, people do seem to be amused when they recognize that the sentence being uttered is an example of the very type of thing that the sentence describes, and often denigrates. Of course, the content of the sentence affects its funniness, as we have seen in all of the families above. Our computer program would do well to demonstrate common minor character flaws, such as laziness, poor grammar, or a minor vice (i.e. smoking). Any one-liner which pokes fun at such character traits while simultaneously exhibiting them would be sure to bust a few guts. Often this technique is better suited for visual humor combined with verbal, as the comedian can then act out precisely the opposite of the advice that he is giving. In its verbal form, this technique is somewhat limited.

Rhyming Games 55

Rounding out the Linguistic Shattered Expectations which play with the overall structure of the sentence is a family which I have called Rhyming Games. It includes such favorites as limericks ("Three Blind Mice") and drinking songs, as well as most lines by Dr. Seuss. 56 As this family was suggested by the construction of the tree, I have not had the opportunity to gather very many examples and decipher their pattern. There is a good possibility that this family is too large to be specified uniquely, and may require further subdivision. The general essence that I am tying to capture with this family has to do with the fact that certain ideas sound funnier when they are expressed as a rhyme, and since most typical English sentences do not rhyme, it seemed likely that the violation of this structural norm (in this case relying heavily on specific words) might have something to do with the humor present.

Sarcasm/Fancy Ways of Saying the Opposite of What You Mean 57

Following the Word Choice branch of the Linguist Shattered Expectation division we arrive at two categories of humor which rely upon the specific wording of the joke for their effectiveness. I have split this category into the Low-Brow and the Smart Ass (or High-Falutin') in the hopes of differentiating between bottom of the barrel puns (as heard on the nightly newscast) and more complex forms of humor.

The Smart Ass category can be sub-divided into two closely related families: Fancy ways of Saying the Opposite and Sarcasm. Both of these types of humor involve conveying a message which is the opposite of the literal meaning of the joke. When enough clues are present (blatant exaggeration, tone of voice, etc.) the audience immediately knows how to interpret the sentence, and often a banal or mundane sentiment (e.g. a complaint) takes on a funny quality when it is cast in this form.

Euphemisms 58

Aside from conveying the opposite of the intended message, wordplay allows the comedian to rephrase commonplace expressions in a synonymous but uncommon manner. In these instances, coming up with a clever way of saying something that is semantically equivalent to its common-place counterpart is an effective method for creating a joke. This method is especially successful when applied to the covering-up of an embarrassing or a bad quality (this family is commonly known as bullshitting).

Simple Puns

Simple puns involve the usage of a single word which happens to have two meanings, both of which are applicable. Puns can also be utilized to create many of the forms we have previously examined, although they can all be constructed without the use of puns. Puns have developed the notorious reputation for eliciting a groan from the audience, and it is somewhat questionable whether people actually regard them as funny or annoying (there is no doubt that people enjoy making them, it's hearing them that is the question). Generally, sophisticated puns (i.e. uncommon puns that most have not been heard previously) are more successful than "low brow" ones, although this is definitely a family which will require a great deal more work before it can be modeled, due to the multiple varieties of its usage.

Running off at the Mouth 59

The other Low-Brow technique is very ill defined, and is also of questionable funniness. It involves the comedian inanely prattling on, about virtually any topic (the more mundane, the better), with no end in sight. The production of a generally incomprehensible, although still grammatical, sentence is sure to elicit laughter in the appropriate context. It would be hard to guarantee a surefire hit with one of these jokes, as they are extremely sensitive the listener's temperament. However, an algorithm which was capable of generating a sufficiently long, grammatically correct sentence, should be able to produce jokes of this family.

Variations on Well Established Inferential Techniques

Koestler's claim that scientific theorizing is very similar to the type of reasoning that goes into the production of jokes works in more ways than one. Not only do both types of reasoning employ biassociative, metaphorical, and analogical techniques, but humor often explicitly co-opts the processes that are "reserved" for serious rational investigation. The following families of jokes all correspond to well studied cognitive processes, such as analogy, problem solving, and hypothesizing, that some might have considered to be the sole province of non-humorous thought. Of course, comedians respect few boundaries, and taboo subjects or areas not thought to be appropriate for humor often find themselves as prime targets for humorous barbs. Considering the importance that society places on rationality and the scientific method, it should come as no surprise that a great deal of humorous material is related to and inspired by it. The very fact that few people expect to hear rigorous reasoning applied to frivolous topics only serves to heighten the humorous impact of the material. Sometimes comedians play off of the expected logical form of an inference and use it "incorrectly", while other times they make an inference which is fully valid in a technical sense, but still manages to elicit laughter.

As these forms have been extensively studied by other cognitive scientists, I will not attempt to provide a comprehensive description of how a computer might generate such forms. Instead, I will bracket these issues and attempt to specify, where possible, the instances in which these forms are funny. Most of these categories may be too broad in scope and should probably be broken down further for future analysis. As mentioned previously, many of these jokes could be categorized in more than one family, but were included here since they also overlap with Variations on Well Established Inferential Techniques.

Logically Valid but Silly Inference, or a Conjunction With Nonsequitur 60

According to the dictates of ordinary logic, if 'A' is true then 'A B' is also true, for any B. While this fact has proven itself notorious to artificial intelligence researchers trying to teach computers to make "meaningful" deductions, this flavor of logic has provided comedians with countless opportunities to poke fun at the consequences of strict adherence to rationality, and our regular violations of it. The humor in this family may have a lot to do with playing dumb, but we can often learn a lot from stupidity.

There are many variations of inferences which are perfectly valid, from a logical point of view, but are fundamentally absurd for one reason or another. The simplest jokes in this category involves assertions which conjoin two statements to make one which is logically valid, but trivial. This technique strongly overlaps with the Biassociation family (see below).

Organized crime in America takes in over 40 billion dollars a year, and spends very little
on office supplies.—Woody Allen

Many involve taking some statements too literally:

On a New York Subway you get fined for spitting, but you can puke for free.

—George Carlin

The guy who invented the first wheel was an idiot. The guy who invented the other three,	he was a genius. —Sid Caesar

Others take a faulty but understandable assumption to its logical conclusion:

Stuffed deer heads on walls are bad enough, but its worse when they're wearing dark glasses	and hair streamers and ornaments in their antlers, because then you know they were	enjoying themselves at a party when they were shot.—Ellen DeGeneris

Finally, some are simply truisms, which are circular, but must ring true nonetheless.

You have to have a talent for having talent.—Ruth Gordon

Good judgment comes from experience, and experience comes from bad judgment.

—Barry LePatner

Initially, I thought that this family could all be described together, but as the examples show, this family is far richer than I anticipated. Working through data of this sort is difficult since a balance must be struck between making the families so small that almost all families are comprised of a single joke and so large that specification becomes an impossible goal. In this case it seems as if an algorithm could be found for very specific brands of reasoning, but not for inferences in general. Actually specifying these algorithms for each of these instances proved to be a greater task than this thesis allows for, but given the limited success of some of the earlier families, there is every reason to think that a computer could be taught to make Logically Valid but Silly Inferences also.

Analogy 61

Many of the jokes that we have already seen implicitly rely upon drawing analogies between two distinct domains. However, there are also a number of jokes which revolve around the idea of drawing an explicit comparison or an analogy. This family is tremendously broad in scope, as many of the conceptual jokes we have seen can be recast in this explicit form. In general, there are a number of basic guidelines for constructing jokes of this type. Once a robust theory of analogies has been developed, as for example the one advanced in Keith Holyoak's and Paul Thagard's Mental Leaps, it is not extremely difficult to construct funny analogies. One common technique (perhaps a family in its own right) involves the comparison of a feature in the source domain to a feature that does not even exist in the target domain (and vice versa). Biassociation can also come into play here, as two domains are mapped to one another through a double meaning, or an outlandish similarity. At this juncture, it would be extremely difficult to find an algorithm which generates funny analogies due to their extremely flexible nature; however, perhaps with a further breakdown of this family into smaller ones, combined with a working model of general analogies, greater progress could be made.

Not-So-Scientific Hypothesis62

Scientists and philosophers are not the only ones who make living by asking "What if?" Many comedians also take the venerable art form of the hypothesis and elevate it to a new level of the absurd. Of course, many hypotheses that were once taken very seriously (i.e. the Earth is flat) have taken on a humorous quality over time, so whatever constraints are found for this family must pay close attention to the context of the knowledge at the time.

Sometimes the very act of making something irrational or trivial sound scientific produces an overall incongruity. Other times the hypothesis is perfectly valid, and yet strikes a funny chord due to the absurdity/novelty that challenges previous assumptions. Hypothesis may also overlap with other families, such as (In)famous Last Words, if the original saying also happens to have been a hypothesis.

Deciding which hypotheses are funny seems to be a task on the order of deciding which analogies are funny. Until the family can be further subdivided, a tentative algorithm involves following the suggestions relating to content in previous families (and in the sections to follow).

Funny/Literal Definition 63

While many consider them to be exceedingly boring, definitions actually provide fertile ground for solid humor. Funny definitions can be built out of a pun on the original word, or out of a humorous way of expressing a real characteristic of some concept. A great deal of humor has been written by choosing a tiny detail that is true, but often considered irrelevant, or by combining this family with analogies,. Playing the dumb guy or the smart ass by taking things too literally (resulting in an absurd or logically incorrect conclusion), is also a good tactic for constructing members of this family.

Problem Solving 64

Problem solving may actually be closer to a riddle than a one-liner; however, many riddles have amusing solutions, and some are short enough to consider here. What characterizes this family is the fact that the punchline is not explicit in the joke, but may only be figured out after a moment's reflection. Furthermore, often if the punchline is given away, the joke loses most of its oomph, indicating that much of the pleasure of the joke is created by the listener trying to figure things out. Its almost like the infantile games where you make somebody repeat something innocent which sounds like something naughty when spoken quickly (i.e. "Fuzzy Duck"). Here the listener is "tricked" into solving a riddle whose solution may be too risque for the listener to have thought up on his own. This family also is far too complicated to be treated comprehensively in this work, but any relevant work on riddle generation would be extremely useful in determining which riddles are funny.

Repetition

Repetition is a somewhat strange family, since it seems as if any random sentence or phrase, repeated enough times can elicit a laugh. David Letterman is the master of this technique, and it is said that he and other late show host, often receive more laughs making fun of their own jokes than they receive for the original jokes. Often this mockery consists in repetition of the earlier material verbatim, until a laugh is heard. A weird family, but perhaps one of the easiest of all to generate. Of course repetition is not always funny, and it is sometimes very annoying, but often this has more to do with the context and the mood of the listener than the actual content of the joke. Exceptions might include direct insults, mockeries and put-downs, although I have also seen these types of sentences fare pretty well under this technique.

Bi-association 65

The major generative heuristic of all examples of humor according to Koestler. While Koestler's formulation of this "algorithm" was rather vague, there does seem to be a distinct class of jokes which does satisfy the gist of what Koestler must have had in mind. These jokes explicitly bring two incongruous elements together through some type of contrived association (wordplay, conceptual similarity, etc.). These two elements are usually so far removed from each other in terms of semantic/conceptual distance that their juxtaposition is often hysterical. A major criticism of Koestler's work involved its vagueness which enabled him to account for virtually all humorous occurrences. However, in a more strictly limited form, biassociations do comprise a leaf on the tree. Even according to Koestler not all incongruous elements brought together are funny (some are quite serious) and in his book The Act of Creation he attempts to specify which are which by exploring the boundary between comedy and discovery.

Observational Humor66

This family of humor is not strictly constrained by some sort of linguistic frame, and revolves around pointing out quirky realities concerning the world in which we live, and our relation to it.

Summary

In this, the most difficult of chapters (one-liners can become tedious if taken in large doses) we have presented the outline of an alternative theory of humor that does not attempt to define humor in one fell swoop. Instead, humor has been carved up into natural, bite-sized, chunks which are far simpler to describe than the entire body of humor.

Ideally, the conditions that describe each family should ultimately take the form of syntactic frames combined with some additional semantic constraints. Using these frames, an implementation of a joke generator could ask you to specify the technique that it should use to construct a joke from the idea that is input. Constructing the correct frames for each family is a difficult task that might be aided by the dynamic development of the program in at the same time as the conditions. That would allow for faster and more thorough testing of the hypotheses instead of trying to produce counter examples out of "thin air".

In a sense, although the definition of humor is disjoint, this theory straddles the fence between a rigid definition and a prototype-based theory. The entire structure is generated by a rule (ways to be incongruous) and each individual family is small enough that a well designed computer program should be able to construct new jokes in that family with a respectable success rate. Trials of the few algorithms specified were conducted informally by hand, and although no algorithm was perfect, no human is funny on every attempt either. Furthermore, the theory does not "rule out" new families of humor, as the disjoint structure is flexible enough to accommodate them as they emerge.

It should be apparent that these frames also correspond to different comedians' styles, and it is possible that human joke production begins with (or at least involves) the specification of a technique in tandem with the creation of the joke. It is also possible that we appreciate a joke partially based on the recognition its form, and then rate the funniness of the joke based on its content. We will return to the ramifications and possible applications of this theory in Chapter 10, and continue now with an investigation of why anything should be funny in the first place.

Part II:

8. But Why is That Funny?

In an important sense, none of the theories we have seen so far provides us with a complete answer to the question "why is X funny". Rather, they simply attempt to point out which things are funny by describing how those jokes accomplish their wit, without giving us a reason why. In some cases it seems as if there is no answer to the why question (explanations eventually bottom out, and things simply are the way that they are), and the which is as far as any theory can possibly explain. It is unclear exactly what type of answer we are seeking to the why question since the nature of humor is as mysterious and uniquely human as love; however, Marr's criterion gives us an idea of the level of explanation that we seek. If funniness corresponds to what we are computing, then in order to fully explain this level of computation our theory must specify which data are funny. For this theory to be complete, it should also address the question of why those data are funny, with the hope of finding a rule which generates and delimits which data are funny.

An answer to a question of this type could lie outside of the range of any theory of humor, as there may not be any reason why we find the things that we do funny. However, we should not allow the possibility of failure to stop us from speculating; after all, we have only suggested that such an answer might not exist, which is a far cry from proving that it doesn't. The following question will help guide this investigation and give it a form which can be grappled with more readily: Are the things that we find funny necessarily funny, or could we conceive of another culture/species that found, for example, congruity rather than incongruity funny?

One of the most important strategies we will employ in answering this question is a comparison of humor to other well studied psychological phenomena. In the process of searching for things which are similar to humor, we will find that no perfect analogy exists. Of course, if two items were analogous in every possible way, they would be identical (or at least isomorphic), so all of our analogies to humor must be disanalogous in some ways. In an analogy between humor and values, nobody intends to suggest that funny things are values, only that they are similar in some important ways. It is important to pay attention to the ways in which things are analogous as well as disanalogous to obtain a more complete understanding of the concept under investigation. Humor does not fit perfectly into the category of an emotion, a piece of sense data, or a conditioned reflex, but it is like them all in certain important respects. Each of the analogies that will be drawn serve to elucidate a particular set of humor's features through an analogy with something in which those features are salient. This technique is a powerful method of brainstorming, since everything is analogous to something in some respect, and it gives us a chance to compare humor with other strange experiences that life has to offer.

You Mean She's Beautiful and Funny Also?

Like the question 'What makes something funny?', the question of what makes an object or an idea beautiful has puzzled philosophers for ages. While someone might propose a criterion such as symmetry or asymmetry, this type of answer is lacking in the same way that the theories of humor are. The follow up question, 'But what makes symmetry beautiful?' leaves us with virtually the same predicament with which we started. Perhaps at this point in the line of questioning we must postulate a bottoming-out foundation point and claim that the perception of humor is much like the perception of color. Red does not look red for any reason, it just looks red because that is how we experience it. The perception of color does not rely upon rules that tell us which sense data correspond to which colors. We discriminate between colors by being able to tell that a thing looks like the experience that we have learned to label 'red' or 'green'.

On the other hand, it is not all that difficult to imagine possible reasons for the evolution of humor. The expression of anger and hostility via superiority humor is obviously a vast improvement for society over actual physical violence, since although a biting remark might embarrass someone, very few people have suffered direct physical harm from humiliation. To this day, humor is used within social communities to maintain power relationships and dominance hierarchies. One need only observe a social group interacting to watch this principle in action, as different people make the same types of cracks, which are responded to very differently, simultaneously reflecting the relative social positions of both the joker and the respondents.

Superiority humor also provides an effective method of social control, as people have a hard time accepting and responding to direct criticism, but seem to handle the criticism far better if it is expressed as a joke or parable. It is important to note that many discussions of political reform, subversion, and criticism take the form of jokes, which thinly mask the serious sentiments beneath their punchlines. This is especially true under repressive regimes, such as the former Soviet Union, where the joke served as a form of underground subterfuge. It is also true in many other contexts, such as William Shakespeare's Fool bearing the message of the truth to King Lear67:

Mark it, nuncle:

Have more than thou showest,

Speak less than thou knowest,

Lend less than thou owest,

Ride more than thou goest,

Learn more than thou trowest,

Set less than thou throwest,

Leave thy drink and thy whore,

And keep in-a-door,

And thou shalt have more

Than two tens to a score.

The role of comedy in social reform and criticism is crucial even in an "unrepressed" context such as modern day America. Jay Leno's and David Letterman's nightly bashing of politicians and the media are poignant examples of the power of humor, and even seemingly innocuous cartoons like the Simpsons often carry with them messages that would be far more difficult to convey without the medium of humor to sugar-coat their critical observations. The humor in these jokes also allows people who are unwilling or incapable of listening to the underlying message to dismiss it as nothing more than superficial entertainment. In some cases, the laughter response may have simultaneously developed as a defense mechanism for some to deny the seriousness of potentially disturbing information, and to provided a deceptive disguise for unacceptable topics of communication.

As far as incongruous humor goes, it is clear that our minds, optimized to process rational, consistent data (or so we would like to believe), needed to evolve a mechanism for dealing with irrational, inconsistent, or ungrammatical input. As the Star Trek character Spock teaches us, there are many ways that we might have dealt with such data. Upon hearing an incongruous or ambiguous sentence, Spock responds with a blank look of incomprehension, the humanoid equivalent to the "Syntax Error" messages that computers report when confronted with incongruity or ambiguity. Humans needed to develop some method for registering and dealing with the fact the not all input is sensible; it would be awfully inconvenient if we "core dumped" every time we encountered something of this sort. Perhaps laughter is indication that we should stop trying to make rational sense of something. It helps us recognize the futility in trying.

Seemingly irrational and inconsistent data are plentiful in the world, and many jokes serve to reveal the absurdities of universal human activities such as sex and eating.68 Cultural dating rituals, arbitrary standards of etiquette, and inappropriate shame are all topics ripe for exposure by the comic, but taboo under ordinary circumstances. Many are also relieved to discover that their private feelings and ideas are in fact shared by others as well, and in this instance one's similarity or congruity with other people may be humorous.

9. Emotionally Attached

The underlying motivation for the preceding line of inquiry is the fact that we have so little access to our reaction to humor that we are unsure of the extent to which conscious69 processing intervenes. In many ways our reaction to a joke is as reflexive as our physiological response to being tickled. Tickling is not a perfect example of a reflex, since as many people have observed, you can not tickle yourself, and some have reported that people only respond to a tickle if it is perceived as a mock attack. Thus, babies will often cry when tickled by a stranger, and only laugh when tickled by their mother (or someone whom they know very well). Simple reflexes are completely automatic responses to stimulus, which often bypass the brain entirely. Since we have not yet discovered a nerve receptor which, without the brain's help, can differentiate between the touch of someone trustworthy and of someone who might be a threat (if the correct force is applied, your knee will jerk no matter who or what hit it), it seems that the response to tickling is more than just simple reflex.

Some have argued that there is no separate cognitive step which evaluates whether or not a sentence is funny after its meaning is apprehended. There is no way to understand the sentence without "getting" the joke, just as there is no way to get the joke without understanding the sentence. To support this assertion they point to the modern day folktale (which is supposed to make us think "Oh yeah, I've experience that") that spies have often been exposed by telling them a joke in their native tongue, resulting in a fit of uncontrollable laughter. This does not prove that humor is a reflex, but it does demonstrate a fact we all know well: sometimes it feels impossible to prevent oneself from laughing, and laughter often slips out before we have had a chance to fully process the joke consciously.

Unlike the evaluation of a scientific theory or even of a work of art, humor is not the sort of thing that we consciously evaluate and then formulate an opinion about. It usually strikes us either as funny, or not, to some degree or another. Not all types of humor are "ha-ha" funny, and often someone is amused but does not outwardly react. However, when somebody does laugh, chances are he actually does think that the joke is funny, and there is little doubt about his opinion to those around him. It is hard to tell if somebody thinks that a painting is beautiful, but a comedian knows instantly if a joke is flop—laughter betrays the soul.

If humor were a reflex, it would be a truly amazing one, considering that the physiological response depends upon a very high level of cognitive processing (including language comprehension). In many ways, humor is analogous to stress, the catch-all cause that medical science blames for every ailment from cancer to heart disease. Stress, like laughter, can be directly induced by physical trauma (i.e. falling into ice cold water), however it can also be induced by the agent's perception of fear, anxiety, or embarrassment. There are many situations which not everybody agrees are stressful (some people may even change their own conceptions of what is stressful over time), and it is hard to conceive of "stressful" being a quality of a situation that exists independent of the agent who feels stressed by it. When people find something stressful, it is not the case that they are perceiving the stress that is out there in the world. Perhaps this is a useful model for thinking about humor.

What these observations amount to is that recognition of humor is somewhere between a reflex and a full fledged decision. Keith Oatley and Philip Johnson-Laird have argued that this middle ground is precisely the domain of emotions and the feelings that they give rise to.

A complex organism has feelings of both bodily sensations such as pain and of emotions such as anxiety, and they are an independent means of guiding behavior. They prepare the organism, not for a specific innate response, but for a general course of action appropriate to the situation. They do not require complex inferential processes. Indeed they are an evolutionarily older method of control and their effects can be rapid and effective.70

The operation of emotions is amorphous and ill-defined compared to a consciously deliberated inference, and this quality directly translates into a faster response time than a costly, complex, explicitly symbolic inference.

Although emotions are primarily non-symbolic it is obvious that they still involve some inferential reasoning, even if much of it is unconscious and not very complicated. The evaluation that a particular piece of sense data is threatening, which in turn elicits the emotional response of fear, needs to be flexible enough to adjust to changing environments where vastly different types of things are dangerous. This evaluation also must be made very quickly, but the organism can not sacrifice the inferential power absent in a reflex. This is where emotions entered the evolutionary stage.

Emotions have the ability to effect perceptions, an assumption which underlies many psychometric evaluations, and as every folk-psychologist knows, your mood affects that nature of your interpretation of reality. Emotional responses are also tempered by social forces, and this is born out in our everyday emotions such as disgust and shame. There are numerous examples of foods (insects, pets, live animals) that are felt to be beyond repulsive in some parts of the world, while they are delicacies in another. Similarly, different cultures place different emphases on what is viewed as shameful (lying, nakedness, etc.) and what an appropriate response to shame should be (ranging from nothing to repentance or ritual suicide). These examples demonstrate that the roles of cognition and emotion are interwoven, and many systems exist which involve the interaction between unconscious inferences and physiological responses, uniting the domains of reflex and conscious decision making.

Emotions also seem to fall into five basic categories: happiness, sadness, anger, fear, and disgust.71 These basic categories seem to span all of the emotions found in social mammals, and any emotions that are (apparently) unique to people can also be grouped under these primary categories. Evidence that these are the only five categories comes from linguistic as well as experimental sources, but this point need not concern us here. What is important is that some theorists have grouped humor as a mode of the underlying basic emotion of happiness (despite the glaringly unique feature of laughter, namely that it is both an innate response to tickling as well as the emotional response to something being perceived as funny). This puts humor in the company of many other seemingly magical phenomena, but at the same time may help explain the difficulty that humorists have had trying to pin down the essence of humor.

10. Conclusion: When Comedy Meets Science-Fiction

The possibility of discovering the conditions under which X is funny is tantalizing, and has led many researchers on relentless quests for such a theory. If such conditions could be adequately spelled out (where X is restricted to verbal humor), it ought to be possible72 to write a computer program which would be able to evaluate the humorous content of any given sentence. Conversely, the best way to test a theory of humor is by writing such a program, or at least specifying how one could be written. The thought of designing a program that takes a sentence as input and returns a value corresponding to its funniness (in the simplest case it would return a message of either funny or not-funny) is intriguing, considering that many people consider humor to be the sole province of human intelligence. Furthermore, this thought experiment raises tricky issues concerning the role that understanding plays in "getting" a joke. Could there ever be a complete theory of humor, or at least of certain classes of jokes? The incorporation of semantic information and common world knowledge should contribute to the advance of research in this direction. Work carried out on the comprehension of stories and texts demonstrates that a great deal of background knowledge is required in order to make the necessary inferences implied by the story. Any computer program designed to evaluate jokes would have to have some method of representing such knowledge.

It also seems that any robust theory of humor would have to be powerful enough not only to evaluate humor, but to generate it as well. A very crude heuristic would simply have the program generate random grammatical sentences, and then run the humor evaluator on those sentences discarding the ones that are not funny. This is probably not the process that human comedians employ to come up with jokes; however, if we had a good enough evaluator function this algorithm would prove effective.

A more challenging project would be to design a program that took as input an idea or a situation, and transformed that idea into a funny formulation. Intuitively, it seems as if some ideas could never be construed in a funny manner, such as a funeral or an operation. However it is hard to find an example of any situation that has not received humorous treatment at some point or another. For example, Tati's Les Vacances de M. Hulot (Mr. Hulot's Holiday) contains a hysterical funeral scene involving a deflated inner tube being mistaken for a wreath, and Levi's is presently running a Television commercial where the patient on the operating table bursts into song to the beat of his own electrocardiogram.

It remains an unresolved question whether any idea can be recast in a humorous fashion73, but many jokes can be robbed of their humorous value if they are told slightly differently, so it is reasonable to ponder the reversal of this process and to expect a comprehensive theory to provide an account of this transformation. Consider the following:

(a) Statistics show that of those who contract the habit of eating, very few survive.

(b) Statistics are often meaningless, people need to eat, and everybody dies.

These two sentences convey essentially the same meaning, and yet only (a) is funny. A good theory of humor ideally should explain how to get from (b) to (a).

According to the theory presented in this thesis, a structure similar to the tree presented in Chapter 7, could help preform such a task. Once the joke idea is determined, the tree could be traversed until a suitable family is found for the presentation of the material. Humans might even use such heuristics in their generation of humor.

A intermediate goal en route to a program which generates humor might be a program which could classify humor into a particular family. If such a program could be developed, it effectively would solve the problem of determining which sentences are funny. If the program finds a family for the input—it's funny, if not—not (barring the introduction of new families). This technique depends upon a robust description of each family, along the lines of a specific syntactic frame, along with some detailed semantic constraints. Many of the semantic constraints might be implemented using existing technology, such as WordNet, and the feasibility of a program which could classify, and in time generate, humor (given the appropriate input), is more than a fanciful pipe dream.

In summary, this theory offers a promising new direction for research on humor and language comprehension, as well as provides an exciting new domain of creativity to be explored, studied, and tested. In a preemptory response to who that find a mechanistic approach to humor and creativity too reductionist, I reply that the question of whether or not creativity can be mechanized is meaningless until we have a model before us of how such an activity might be computed. Once we isolate the components of a phenomenon that can be reproduced mechanically, we will then be able to judge if there is anything left that remains unexplained. However, until we attempt to explain the ineffable and demonstrate where our theory falls short, our conjectures concerning the nature of creativity are merely speculation. In writing this thesis I hope to become part of this team of explorers, and to make my own creative contribution without ever forgetting the importance of a good sense of humor.

This thesis represents my own work in accordance with University regulations.