A new perspective on laughter and humor

Laughing                                                                                                                                                                                                                             At first glance, laughter appears to be less important to our survival than crying. However, as human laughter has its counterparts in the panting "laughter" of chimpanzees .(Provine 1996) and the high frequency squeaks of rats, (Panksepp 2003) it is highly likely that the evolutionary forerunner of laughter was of survival value to some mammals including our hominid ancestors. I must make it clear at this point that I use the word "laughter" to mean human laughter. The neural processes that produce the laughter vocalization in humans I consider to be the same as those in animals that produce similar vocalizations, but the underlying psychoneurological processes I view as having changed with changes in the complexity of the hominid cognitive and emotive systems. Human laughter can ultimately be traced back to the play fighting of mammals in which a vocal displacement of emotive activity allowed them to practice manoeuvres without harming each other. The circumstances in which chimpanzees "laugh" are limited to play-fighting, tickling and chasing, and although the "this is a fight / this is not a fight" conflict may have laid the foundation for the joke format, it is obvious that the wide variety of circumstances in which humans laugh requires further explanation.

Each habitat demands specific survival strategies from the animals that occupy it, and once our hominid ancestors began to spend time on the open grasslands emphasis would have been placed on certain behaviors. The strategies for food gathering and defense in the forest differ greatly from those on the grassland, where a change to a more omnivorous diet (Sponheimer and Lee-Thorp 1999) and a lack of immediately accessible escape routes would have meant the need for greater cooperation and a unifying system of control within the hominid bands. It is significant that the forest dwelling bonobo chimpanzees live in loosely organized, female dominated groups (Stanford, C. 1998) but in line with most ground living primates, the hominids were probably led by a single experienced alpha male. In open country it would have been essential for the alpha male to rapidly assess the severity of threats so as to deter any premature action on the part of individuals that might precipitate an aggressive response from potential predators. A novel event, or one perceived as potentially dangerous, would have induced a fear response in all the apes, including the alpha male, but in situations where no immediate fight or flight response was perceived by him as appropriate, the deflection of emotion into an audible and contagious displacement activity would have been particularly effective in calming the members of the band and preventing panic scattering. (Ramachandran 1998) In line with ideas concerning laughter in modern Homo sapiens, as well as being a useful tool in inter-specific interactions, a contagious staccato vocalization displacement activity would have been effective in calming individuals during intra-band conflicts. In these situations bonobo chimpanzees employ sex as the displacement activity (de Waal 1995).

It is generally accepted that staccato vocalization (laughter) existed long before the advent of language and the cultural aspect of our evolution it was instrumental in bringing about.( Gervais and Wilson, 2005) In the past, emphasis has been placed on the study of laughter inducing verbal constructs within the adult cultural milieu, but if we are to fathom the true nature of what we call "humor", we must first explore other avenues of study that have a bearing on the natures of laughter and crying. Headway in these endeavors has been slow, due to a top-down approach, which, at times, views laughter as being an almost incidental response during the processing of "humorous events". A top-down approach immediately runs into problems as it becomes bogged down in the seemingly unfathomable contextual complexities of adult human laughter and is further compromised by a failure to recognize verbal humor induced laughter as an aberration of the basic laughter process. Humans have greater emotive control and a massively more complex cognitive system than their hominid ancestors, and it is these changes in our emotive and cognitive systems that have produced the complexities and aberrations that mask the basic nature of laughter. When the different types of laughter, and the different contexts in which laughter occurs, are considered, it appears that the basic laughter process has been exapted to serve different functions in modern Homo sapiens.                                                                                                                                                                                                As laughter predated language in our evolution, it is obvious that verbal humor plugged into a response system that already existed. It is therefore my contention that we will arrive at an appreciation of the phenomenon we have termed "humor" by studying laughter. This means that we must start with the neurology of laughter and work upward to cognition and linguistics, and on a temporal level, begin with our hominid ancestors, and using the data we have on laughter, attempt to map out its its evolution.

The basic process of laughing can be defined as the displacement of emotive neural activity, on the fear (negative) side of approach and avoidance motivations, when it is denied expression by opposition or redundancy.

Unlike crying, where the precipitating stimulus is normally an actual, or a memory of an actual, highly emotive external event, laughing is often a response to internal motivational conflict, or in a similar manner to crying, a sudden redundancy due to changes in circumstances. Again, unlike crying, laughing normally only occurs during an event if the degree of fear being engendered does not swamp the opposing motivation, in general, limiting laughter to cases where the danger factor is low, or perceived to be so. In circumstances when the danger factor is high, or perceived to be high, people may laugh immediately after the event.

Our organismal reaction to falling is fear, and a young child's screams of laughter when being tossed into the air by a trusted adult is an indication that the reflex fear response is being opposed by the child's tacit knowledge that he is in no danger. If the child is tossed by an adult with whom he is merely acquainted, he may not laugh at all, and as his fear level rises unopposed, the form of displacement becomes a communicative crying for help.

How do we account for the facts that some individuals laugh when in extreme danger, and some Cambodians, having escaped Pol Pot’s reign of terror, reacted with laughter when told of further atrocities? At times, a general state of nervousness can be relieved by a spontaneous displacement of emotive neural activity into a short burst of laughter, probably facilitated by a small window of opportunity brought about by a momentary cognitive shift (a change from one line of thought to another (Latta 1999)). Nervousness, a muted expression of fear, is a common enough feeling that builds up before we face challenging events. Extreme fear is distinguished not only by its intensity but by the fact that the fear evoking situation is not usually expected and is so beyond the normal it can seem unreal - "It was like being on the television", as some people say when they have been in unexpected and dangerous situations. During the ordeal, others might say, "This isn’t happening!", or, "You’re joking !". The brain will perform all sorts of manoeuvres to escape a dangerous situation, even to the point of denying that it is happening. Some people are more prone to denial than others, and they are the individuals whose brains attempt to view distressing events as though they belonged to a different dimension. Again, it is a cognitive shift, from an appreciation of the event as real to a fictitious interpretation, that presents a time window in which the emotive neural activity of the fear response becomes redundant and is displaced through laughter. For those of us who live in comfort in the West, a report of an atrocity taking place on the other side of the world can produce a large emotive response as such events are not the daily norm. We do not react with fear, as we are unlikely to suffer the same fate, but with anger, which, in the more sensitive of us, may give rise to tears, and we naturally expect that the Cambodians would have reacted in a similar manner. The reaction of the Cambodians, who had lived for a long period of time in helpless resignation, would have been fear, and in people for whom fear had become the norm, the displacement was in the form of laughter. Although children in South East Asia are often encouraged to laugh when feeling sad (Frye and McGill 1993), inappropriate laughter that takes place in tragic circumstances and seemingly causeless spontaneous laughter are typical of individuals suffering from long term stress (Hempelmann 2007).

People laugh a great deal in social situations and especially in the presence of their friends. The ability to displace emotive neural activity into staccato vocalization probably enabled our hominid ancestors to lower stress to levels appropriate to the situations in which they found themselves, and social laughter performs that function today. Although our normal activities require a mind set on the aggressive side of approach and avoidance motivations, this does not mean that on an organismal level the environment is not continually being tested by the brain areas that mediate for fear. Long before we are conscious of certain aspects of the environment and bring our cognitive faculties to bear on them, the amygdala of the brain has already interpreted the situation in terms of basic responses and determined the appropriate level of emotional activity. However, our prefrontal lobes are capable of inhibiting these responses if they are inappropriate on a cultural level.

From the time the animal world shook off the shackles of limiting stereotypical responses, it was faced with the problem of greater choice, and thus ambivalence and vacillation. The evolution of language and abstract thought only complicated matters as it greatly increased the field of possibility and our ability to imagine and fabricate (Kozintsev and Butovskaya 1999). When intelligence took over from instinct as the primary tool for dealing with the world, the new mental and physical experiences, made possible by our developing brain, required a new response to novelty. If experience did not fully allay our fears concerning particular objects and events we demystified them by naming, ritual, interpretation and rationization. The answer to ambivalence, doubt and fear was culture - a commonly held, and vigorously defended, system of ideas that lays down the way members of a group should think and behave. The cultures into which we are born are mental constructions, designed to maintain order and hold fear at bay.     

As we confidently act within our self-made mental and physical environments, functioning in the background, and for the most part denied access to consciousness, is part of the brain that is still interpreting the world in organismal terms of survival. This means that we are much more anxious and defensive than we acknowledge when coming into contact with other people. There may be an under-current of physical threat when meeting a large stranger, and as we have, in most circumstances, adopted words instead of actions to express ourselves, we are guarded in what we say and highly sensitive to what is said to us.

Many people laugh when they talk to babies. The probability is that their normal defensive brain set is found to be at odds with their knowledge of these small and defenseless individuals. We exhibit a similar relief response when we meet friends. The normal defensive and readiness emotive states become redundant when we are in the presence of people we know well and trust. The laughter of a young child on the return of a primary caregiver after a short separation can be viewed in a similar light. The reappearance of a trusted individual makes the neural activity underlying separation anxiety redundant - laughter acting as an agent of displacement and also inducing laughter in the caregiver, which aids in the reaffirmation and strengthening of mutual bonds.

Duchenne and non-Duchenne Laughter                                                                                                                                                                        A mention must be made here of Duchenne and non-Duchenne laughter. Duchenne laughter is seen as being involuntary whereas non-Duchenne laughter is a more controlled form of laughter and lacks a strong emotional basis. The laughter of game-show hosts and salesmen is often of the non-Duchenne type. It probably evolved to allow hominids to use its affect-inducting properties to strategically influence others in social interactions. ( Gervais and Wilson, 2005) There is disagreement amongst researchers concerning which laughter evoking events should come under the heading of humor. I agree with Provine (Provine2000), when he views the laughter of friends when chatting as not always being laughter of a humorous type ( the mechanism of its evocation differs from that of a joke), although we do describe such situations, in cultural terms, as "good humored". During a meeting of friends much of the laughter would be of the non-Duchenne type. However, even in the absence of any verbal exchange that engendered conflict in the brains of the participants, some of the laughter would be genuine, Duchenne laughter, especially when the participants initially meet. This would come under the "change of activity" heading; and there might be some "humorous" laughter if, as young men are wont to do, they insulted each other and engaged in mock fights.

I view laughter in modern Homo sapiens as evolving from a basic fight or flight displacement activity, and in the process, being co-opted by different systems in the brain to serve specific functions. Duchenne laughter takes place in a variety of different situations, but if I were to use the word "humor" at all, it would be limited to events that induce conflict which is then resolved by the emotive brain activity that sustains it being displaced into laughter. There would also have to be a further distinction between physical and verbal "humor", between slapstick and joking. Again, if I were to use the word "humorous" , it would not cover all the pleasant situations in which laughter is elicited . The situation where laughter is induced by the redundancy of an emotional state, I would not see as belonging to humor, nor the situations where drugs and alcohol cause spontaneous outburst of laughter. There is also an aspect of intentionality in deciding whether an event is viewed as humorous or not. Is a man slipping over and evoking laughter in those observing him to be viewed as a humorous event merely because it evoked laughter, or can the event only be classified as humorous if the man, or a clown, intentionally slips over?

The problem with the concept of humor                                                                                                                                                                      Before we can apply the idea of laughter as a displacement activity to humor theory we must first strip humor theory of its excess conceptual baggage and dispense with the erroneous assumptions that have, for a long time, hindered progress in the field.

Pleasure, pain and stress                                                                                                                                                                                              As laughter is usually associated with pleasure - seen as causing, or expressing, a feeling of pleasure - an examination of the nature of pleasure should give further insight into the nature of laughter. Ask people what activities they indulge in for pleasure and the list you collect will be extremely long and the entries diverse. Some activities can only be enjoyed on ones own, others in small or large groups. Many activities are goal oriented, others are not. Some require a large mental input, others are physical, and some have both mental and physical aspects. One person may find another person's pastime irritating or even painfully boring and any attempt to discover a common positive element in all the activities, other than the participant’s insistence that their pastimes are pleasurable, will fail.

The quality of the feeling of pleasure experienced while indulging in pastimes also varies. We cannot compare the exhilaration felt by the sportsman to the excitement of the birdwatcher when he sees a rare species, or the tranquillity of the individual reading a book on the lawn on a bright summer’s day. The unifying aspect of pleasurable activities seems to be encapsulated in the comments, "It takes me out of myself", and, "I lose myself in it". The unifying element is not to be found in the activities themselves, but the ability of the activities to afford the mind an escape from the self and all its attendant anxieties. It appears that the only unifying aspect of pleasurable pastimes, which is not subjectively based, is a negative one - the deflection of mental activity away from brain areas that engender stress.

The following may appear to be a truism, but at least one requirement for us to experience what we have called "pleasure" seems to be the absence of pain ( in the processes and situations to be considered here, meaning mainly emotional pain, fear, anxiety, remorse, sorrow, etc.) The next question that must be asked is whether the absence of pain is the only requirement for a feeling of pleasure to be experienced?

Although we view pleasure as being positive (desirable), the possibility is that, in a neurological sense, it is negative. Pain can be viewed as the positive of the pleasure/pain duality, and pleasure the conscious appreciation of a change in brain state brought about by the fulfilment or inhibition of the motivations that sustain the neurohormonal substrates of stress. In other words, emotional pain is the conscious appreciation of being over stressed and pleasure the conscious appreciation of the lowering of stress (Becerra, L et al 2001). It is possible that the rats, in Old's classic experiments of the fifties, were not registering what we have erroneously characterized as an entity, "pleasure", but were locked into the continuous, stressless, end game of the stimulus-> response-> satisfaction, sequence. They may have continued to press the lever that sent an electrical stimulus to the septal area of their brains because it immediately induced the neurochemical substrates of satisfaction and left lever pressing as their only motivation. Recent research suggests that dopamine is not the "reward" neurotransmitter, as once thought, but mediates for "wanting" rather than for "liking". It is very easy to mistake obsessive wanting for liking and therefore assume that approach movements are influenced by anticipated "pleasure" (Winkielman et al, 2003; Pecina et al, 2003).

If those of us who are in an advanced state of decrepitude concentrated on our bodily and mental states we would be able to come up with a whole list of sensations such as: a slight tooth ache, an old wound giving pain, arthritis in the knuckles, a slight feeling of anxiety accompanied by visceral activity. We are distracted and unaware of such sensation for the greater part of the day. Now, if all the sources of these sensations were somehow shut down while we were in a normal state of distraction, there is little doubt we would immediately register the change and report it as a pleasant feeling . The reports of pleasurable feelings induced by drugs generally fit into the categories of "enlivenment" and "euphoria". There is a difference between a report of an event being pleasant (as with the variety of pastimes) and a report of feeling pleasure. Enlivenment may be reported as pleasurable, but the feeling of enlivenment is not the feeling of pleasure. Without the attributes of a complex event to complicate the situation by introducing psychological biases, or concomitant feelings to which we can attach the word "pleasurable", a drug induced feeling of euphoria is probably as close as we can get to an unadulterated feeling of pleasure. The anterior cingulate cortex is one area of the brain were physical and emotional pain are registered (Panksepp 2003). It is also a site of the analgesic action of opiates, the administration of which typically induces the stressless state we call euphoria.

Although stress is sometimes, and erroneously, viewed in terms of arousal (Cox and Griffiths1995) the aspect of stress most pertinent to the study of laughing, crying and humor is stress in relation to action. Although the lay person may immediately associate emotions with feelings, feelings merely signal that neurohormonal changes are taking place. An emotive process is one in which the body is readied for action. We enter a state of high stress when this neurohormonal readiness is maintained for long periods of time, or is continually being induced, but denied expression in action. We are in a continuous state of stress as the brain's cognitive mapping of the environment is matched by an emotive mapping, which interprets cognitions in terms of potential action. Emotive activity is taking place all the time as it is necessary for appropriate decision making in response to cognitions, but the brain works on a "need to know" basis, and only in a limited number of circumstances, often when extreme action is required, do we become aware that emotive processing is taking place.

It can be seen from the four quadrant model of mood, below, that pleasure is associated with the lowering of stress, and mental pain with the increasing of stress.

High arousal and high stress (anxiety),

High arousal and low stress (pleasant excitement),

Low arousal and high stress (boredom),

Low arousal and low stress .(relaxed drowsiness). (After Cox and Griffiths 1995)

We report the most pleasure when arousal is increasing and stress is decreasing. Children will exhibit the exhilaration we have called "unbridled joy" when indulging in activities that cause a reflex fear response which is quickly opposed by the knowledge/faith that they are in no danger. (As in being chased or tossed about) .In line with my definition of an emotive process as one in which the body is readied for action, I view neither laughter (which is sometimes cited as an emotion in popular writing) nor exhilaration as emotive states. Laughter could in fact be viewed as anti-emotional and represents the voiding of emotive activity, and exhilaration as a conscious appreciation of the effects of the hormones and neural transmitters that sustain arousal, again when emotive activity is being released. The same arousal state would be deemed to be pleasant or unpleasant depending on whether stress was decreasing or increasing.

An individual's history is not just an archive of cognitions but an archive of cognitions with emotive underpinnings that give them meaning on both a cultural and organismal level. The past, present and future are all mapped out in this manner, and all have the potential to induce high levels of stress. Actions that should have been taken in the past, anger that should have been expressed, things that need to be done immediately, but are deferred, and things to be done in the future, that may involve difficulties, all give rise to stress because, for various reasons, action is, or has been, denied. As we go through life we build up what might be termed an "emotive debt", event specific, unexpressed emotions that are continually reawakened, but not necessarily brought to consciousness. In extreme cases, this can lead to physical and mental ill-health (Merali, M. 2007) and precipitate drug addiction (Cuomo, C, et al. 2008), or if the emotions are inappropriately expressed, to criminality, as in the cases of abused children becoming abusing adults ( Campbell, D, et al. 2001).

Action, cognition and language                                                                                                                                                                                       Most of what is written on the subject of humor concentrates on verbal humor and its social and medical effects. Not all humorous events entail language, but if we are to fathom how language in a particular format evokes laughter, we must first grasp the connection between language and the reality we believe it conveys.

If our cognitive systems, in concert with our emotive systems, are to act as efficient agents of our survival then they must, for most of the time, convey reality with a fairly high degree of accuracy. Our ability to consider situations and plan future actions demands that reality is somehow simulated in the brain, which, during our evolutionary history, would have entailed the development of a system that utilized processes that gave rise to meaningful movements, such as body maps and stored sequences of muscular contractions (Cruse, 2003). Like a flight simulator, which never leaves the ground, the brain is able to simulate, without actually instigating action, and so is able to practice, plan and invent. Language represents a natural progression as it is an extension of this initial exaptation. The development of language did not require a completely new system of neural processes as it arose from the association of sounds with aspects of the world that continued to exist in a simulated form even in their absence. Language was only made possible by the evolutionary changes by which cognition and emotion were separated from action. In the beginning, language probably described the world in purely metaphorical terms, but finally, when, through feedback, our ability to conceptualize reached the point where we could contemplate language itself in terms of cognition, we developed logical thought by a further separation of cognition and emotion.

Language, even in technological societies, lies closer to that of the hunter-gatherer than the logician, and as Pinker (1997) has pointed out, we use space and motion as a metaphor for abstract ideas, even when describing things that are static, as in the sentence, "The bruise went from dark red to black". This is not surprising as language conjures, and is conjured by, a simulation of a reality defined by movement and change. Language has meaning on both semantic and emotive levels. Different situations have different emotive flavors and are mapped in terms of potential and appropriate action. Verbal communications are mapped in a similar manner, the emotive flavor changing in response to the ideas expressed, like an appropriate musical backing to the lyrics of a song.

Specification is relatively new development in the evolution of cognitive systems and is a function of language. How new is demonstrated by our continuing use of metaphor, and more specifically by words such as "glas" in Welsh, which covers shades of green, blue and grey. There is a word in Japanese that is used in a similar fashion, "aoi" , which means green, blue or pale -presumably because vegetation and the sky are the continuous backdrop from which highly colored flowers, birds and insects stand out. The separation of colors from contexts is obviously relatively new, and such distinctions have their neural correlates in the differences in the way information is processed in the left and right hemispheres of the brain. The history of both language and science is the history of specification, but on an organismal level, below the neural systems that support language and culture, the brain functions within broad contexts and emotively maps general forms into which specific instances fall. ( Loss is the general form, a child losing a toy to another child, or the death of a spouse, are specifics.)

We make a grave mistake when, for want of knowledge, precise definitions and an appropriate lexicon, we parade intellectual analyses as the neural processes behind certain phenomena. This, of course, is unavoidable, but we must be aware that the "story" of what we believe is taking place, couched in terms used in everyday cultural intercourse - outside coherent space/time frames and unrelated to other pertinent fields of enquiry - may be little more than an application of the assumptions and biases required to validate existence within a cultural milieu. The cultural does not necessarily map onto the organismal.

Humor theories                                                                                                                                                                                                                  If, indeed, the central and most pertinent question concerning humor is: why do certain utterances, pieces of writing and events induce people to break out into the staccato vocalization we have termed laughter?, then it is obvious that each of three main humor theories focus on particular stages and aspects of the sequence of events that take place during a laughter evoking episode. To illustrate this, consider the steps that take place during an effective joke telling episode.

The aggression/superiority theory (Heyd 1982)(Gruner 1999) suggests that we laugh at the misfortune of others, or those who we consider beneath us in terms of power or social standing, and humorous situations are viewed in terms of aggression and competition. This theory, that focuses on the motivational (a) theme and content (b) (c) and emotional (e) aspects of a humorous event, is based on an erroneous view of laughter. Contrary to the superiority theory, the evidence from studying the basic laughter response in children and adults suggests that it is emotive activity on the fear side of approach and avoidance motivations, and not on the aggressive side, that is central to the evocation of laughter. Power and standing can be maintained by approval and respect, and only the fearful maintain power through aggression. Laughing at the less fortunate is not an act of the superior but of the frightened. We cannot inhibit the mental process we term empathy - it is an indispensable facet of comprehension - and because those people who laugh at the unfortunate cannot help putting themselves in the situation of those they belittle, the emotive weight behind their laughter is fear. These individuals have consciously distanced themselves from the those they see as their inferiors; they do not sympathize with the less fortunate, but cannot escape the innate process of empathy, which places them in the very state they find repulsive.

The popular incongruity-resolution model (Kant 1790) (becerra and Raskin 1991) attempts to describe how humorous material is processed in terms of linguistic/cognitive theory (b) (c) (d) (f), and although efforts have been made to reconcile the theory with neurological data (McCrone 2000), the basic concepts remain isolated from important biological considerations. The theory appears to be an intellectual extension of the common idea of "getting" jokes. The incongruity-resolution theorists believe humor is created by a multistage process in which an initial incongruity is created, and then some further information causes that incongruity to be resolved (Ritchie, 1999). It is possible that they are making no distinction between a post-delivery, conscious analysis of joke mechanisms and the neurological processing of jokes of which we are completely unaware. Even if the kind of analysis they suggest does take place during and immediately after the delivery of the joke, this does not lead to a convincing neurophysiological explanation of the evocation of laughter. The theory also falls down when considering many jokes of a sexual nature and non-verbal laughter evoking situations, both of which resist this form of analysis. However, the idea of incongruity in general does suggest the inducement of incompatible neural entities, which gives us further insight into the nature of the laughter process.

The relief theory of humor is a "why" rather than a "how" theory, and basically views humor as been instrumental in the release or replacement of what has been variously characterized as "psychic energy" (Freud 1916)(Spencer 1860) and painful emotions(e) (g) (h). Relief theories deal with the general effects of laughter inducing events and give little insight into the neurophysiological source of pleasure or the nature of the laughter process.

A displacement theory of laughter - in essence a theory of humor - combines aspects of the relief theory with the basic concepts behind incongruity theories, although, in line with classic displacement activities, displacement is viewed as a response to irresolvable conflicts. A laughter theory of humor might be viewed as reductionist by those who take the broadest view of what constitutes humor, but it accommodates all the major theories and explains how they can contribute to a laughter evoking situation. It explains the neuro-psychological basis of the superiority theory, rectifies the erroneous assumptions of the incongruity resolution theory and places relief theory on a firm neurophysiological footing.

Jokes                                                                                                                                                                                                                              The essence of the joke event is that it is devoid of immediate rational analysis. One does not advise the joke teller that lions can't talk when he starts his story, "This lion said to an antelope...."; indeed, any discussion of a joke during and after telling is frowned upon. The enjoyment of all fictitious art is that we give ourselves up completely to it and suspend disbelief. Brevity is the soul of wit, because the less said the more imagined and felt. Explanation is kept to a minimum in jokes as it swings thought processes towards the rational and specific and away from the divergent processing on which the imagination feeds. Consider the following joke.

A concert pianist travelled to Africa in a bid to prove that music had the power to sooth the savage beast. With the help of native bearers, he set up his grand piano in a small clearing beside a river, and began to play. One by one, animals appeared, and soon he was surrounded by lions, giraffes, antelopes, warthogs and leopards, all sitting peacefully together swaying and tapping their feet. The pianist had just started to play a second piece when a crocodile splashed out of the river, grabbed the man, dragged him into the water, did a death roll and rammed him under a submerged log. An agitated lion ran over to the water's edge. "Why in heaven's name did you do that?" he asked. The crocodile cupped a foot to the back of his head and said, "Eh ?"

If we omit the last three lines and add, "because it was deaf" the joke is dead. The explanatory sentence inhibits the unconscious non-verbalized appreciation of the situation and the unconscious intercourse between the different areas of the brain that are making their own sense of the verbal input. It seems unlikely that during a process that demands a suspension of rational analysis part of the brain is doing a quick intellectual scan of the joke material as the incongruity-resolution theory suggests. However, the brain is so versatile, and can function simultaneously in different areas and on different levels, that such processing is not out of the question. What I see as being out of the question is natural language being able to interface directly with the processes that give rise to laughter.

Language had to evolve on the back of a highly developed cognitive system working in concert with an emotive system that interpreted information in terms of appropriate action. There is no reason to assume that the basic processes that triggered staccato vocalization in our pre-verbal, hominid ancestors are not the same processes that trigger laughter in modern Homo sapiens. If, as suggested, laughter is a form of displacement activity, that in the past was induced by any situation that involved motivational conflict, then it is highly probable that the specifics of jokes are also unimportant as far as the laughter process is concerned. It is not the wording of the joke that is important but the way the mechanism of the joke juxtapositions the emotive aspects on a much lower, organismal level.

With a little rewording, almost all of the authoritative material ever published on the topic of humor can be fitted into a coherent theory. Without a unifying aspect operating below the level of language, historically writers have been free to highlight what they see as the most important characteristic of humor and put this forward as representing its true essence. The problem has been that the specificity that language imposes on our thought processes, and is required for intercourse in the cultural milieu, is not applicable at the deeper levels of neural processing. It would be grossly inefficient to have a neurophysiological system that reacted to specific situations, and on an organismal level we recognize only two broad categories, situations that help and situations that harm; and have three basic responses, approach and avoidance and freezing. Human lives are characterized by though, language and the complex social milieu that these cognitive and communicative phenomena have brought about. We tend to forget that although thought may guide our actions, it is action not thought that is essential to our survival. Everything we think, say or hear is ultimately measured in terms of action or potential action. The complexity imposed by the specificity of language can be seen as being channelled down a funnel of processing - representing the evolutionary history of language and cognition ( through the more general forms of representation, metaphoric generalisations and visual metaphors) to the deep emotive, organismal level, where everything is interpreted in terms of motivation and action.

The conflict in the crocodile joke is modal in nature. Most joke stories are fictitious, but only some are in fantasy mode. While listening to a fantasy joke, the brain can very easily stay in fantasy mode as long as the joke is describing action, but as soon as questions are asked, or explanations given, there is a tendency to slip into reality mode. The word "why", (for what reason), is particularly reality bound. If the joke had ended, "because it (the crocodile) was deaf", the processing of the joke would have quickly ceased, but by hinting at the answer to the question asked by the lion (the foot cupped at the back of the head) the unconscious processing continues and the brain is directed to go through a reasoning process within the rationality/reality mode. The format of the joke produces a modal conflict by inducing the rational mode of thought to justify the fantastic.

The type of joke and the type of conflict is irrelevant to the evocation of laughter, which will occur as long as a neural vacillation akin to motivational conflict is induced. There are many jokes that produce conflict by violating cognitive norms. Veatch (Veatch, 1998) expresses this idea in the form of the violation of moral principles. Cognitive norms are the beliefs and knowledge an individual holds to be correct through perception, tradition, rational thought and faith. As far as the mental processing of joke material is concerned, whether the individual is correct or incorrect in his beliefs is irrelevant, he will react emotively if the joke content violates any of his cognitive norms. Cognitive norms can be divided into two classes: objective norms - those shared by the whole of humanity (Such as an appreciation of the space/time continuum and the knowledge that objects don't fall upwards) and subjective norms - ideas accepted as correct but peculiar to individuals and cultures. Although the two jokes below appear on the surface to be very different, their effect depends on the violated of the same cognitive norm.

An American tourist came across an unusual stall in an Irish market. He spotted a human skull, and asked the stall holder who it had belong to. The Irishman replied it was the skull of King Brian Boru himself. The tourist, being of Irish stock, bought the skull and took it back to the States. Some years later the American returned to Ireland and came across the same stall holder who was in the possession of a small human skull. The American asked whose skull it was. The Irishman replied "The skull of King Brian Boru himself." "But I purchased Brian Boru’s skull from you four years ago!", protested the man. "Yes, said the Irishman, "But this one is from when he was a boy".

An Australian and his faithful dog became lost in the outback, and after a week without food the man reluctantly decided he would have to sacrifice his lifelong companion. He built a fire and roasted the animal, piling up the bones as he devoured the meat. After he had finished he gazed pensively at the pile and said, " Blacky would have loved those bones".

Both these jokes depend on a violation of the space/time continuum. For the small skull to have been that of Brian Boru he must have been dead and alive at the same time, as he lived to produce a large skull. Without time travel, no one can be dead and alive at the same time, and for the Australian's dog to have appreciated those particular bones, this would have had to have being the case.

The most important aspect of many jokes is allusion - ideas and situations hinted at but not directly stated. It is thought that allusions are processed in the right brain, a fact that immediately suggests another form of modal conflict between the processing of information by the right and left hemispheres. However, it is the way allusions are registered that make them an important tool in the inducement of laughter. The listener's brain is not directly given all facts of the joke situation verbally and is enticed to fill in the gaps. A falsity heard is immediately rejected if it is contrary to the listener's knowledge and accepted norms, and the effectiveness of an allusion lies in the fact that it is the listener's brain itself that generates the ideas and images and so a processed allusion has the weight of a conclusion.

It would be interesting, but fruitless, in the context of this essay, to list all the different types of jokes in respect of the modes and systems that are brought into conflict, but sexual jokes are a special case and deserve comment. We can only describe neurological events in "story" terms, as words are unable to convey the reality of processes that entail thousands of serial electromagnetic events taking place in various areas of the brain. We can intellectually analyse jokes and give explanations in terms of content and mechanism, and it is in the area of mechanisms that sexual jokes differ from other kinds of joke. Consider the following sexual joke.

Letter to the Agony Aunt of a women's magazine.

Dear Aunt Martha,

I have a problem. It concerns my husband, who demands I have sex with him at all times of the day - often at the most inappropriate moments. I have talked to him about his lack of consideration, but to no avail. Have you any advice on how I could break him of this distressing habit.

Thank you.
Bessie Brown.

PS. Please excuse the wobbly writing.

As with many sexual jokes, we can discern an allusional aspect that conjures up the sexual act, but having implanted an image in the reader's/listener's brain, with what does this conflict? Why do we laugh at sexual jokes? We cannot get anywhere by stopping at a link with embarrassment, as sexual embarrassment is unique to human beings, and we should ask the question: Why are we embarrassed by sex ? We can only answer this question by putting together, as best we can, an evolution of sexual behavior in the hominids, guided by the few clues history has left us. The first two questions to be answered are: why does such a cerebral creature as man think about sex so often, and why does the human male have a sexual organ which is relatively much larger than the other apes ?         Sex may well have been the central controlling factor in the organization of early hominid troops, and before language (verbal symbolism) genito-anal symbolism aided the coordination of the social group. The sexual control of stress in the Bonobo (pygmy chimp) (Stanford, C 1998), adds weight to the theory, but other than the large male penis, what evidence is there that genito-anal symbolism was involved in the control of early hominid behavior? The behavior of present day primates suggests that so-called perversions (homosexuality, coprophilia, sado-masochism, flashing etc.) have a long biological history. It is generally accepted that there is a large power component in the motivation to rape (McCabe and Wauchope 2005) and the genital displays of primates (Guthrie 1976) are mirrored by the flasher's vain attempt to demonstrate his dominance.

Although we regard faeces, urine, saliva and even blood with distaste, some of the worlds hunter-gatherers consider anything that comes from the body as having special powers. It is possible to view the naked, faeces smearing displays of powerless individuals in prison as a desperate last ditch expression of bodily power. The life and sexual exploits of the Marquis de Sade (de Beauvoir 1951) suggest he was a man who had rediscovered in himself the seat of bodily power, and it is significant that he rejected the unemotional, abstract, concept based power of the church and state. Sado-masochistic practices also suggest a history of sexually based power within a changing hierarchical social structure. As the frontal lobes of hominids increased in size, and language evolved, the nature of communication and power shifted - genito-anal symbolism gave way to verbal symbolism and power gained an intellectual component. Defecation, urination and sex are activities we have been unable to civilize and we never really get beyond our childhood assessment that love-making is the slapping together of smelly genitals: as Yeats expressed it, "Love has pitched his tent/ in the place of excrement." There are sexual jokes in which there is no discernable mechanism at all; none is required, as our very existence comprises a functional duality and we vacillate between the organismal and the cultural - between the ape and the angel.

Sexual jokes, on the whole, lack the format to produce conflict directly. They depend very much on an allusional aspect, as demonstrated by the Dear Aunt Martha joke. Like most jokes they elicit the greatest volume of laughter when narrated rather than read. It is hard to separate the reasons for this. A number of possibilities are: as laughter is a communicative phenomenon, it is more likely to take place in a group setting; being social creatures, our emotive systems are particularly active in group situations; some of the laughter is of the non-Duchenne type, resulting from the reluctance on the part of listeners to cause the narrator embarrassment; the relaxing atmosphere of the joke telling context facilitates the release of stress and, probably the most important aspect of narrating a sexual joke, the presence of other individuals when a particularly private aspect of human life is the centre of attention. Children do not require embarrassing topics to be packaged as jokes to make them laugh and will often giggle at the mere mention of sex or bodily functions.

Below is one of the few sexual jokes I have found that does not depend on allusion, has no internal mechanism to cause conflict and gives the full description of what is happening.

A woman finds that her sexuality is waning, and seeing an advert in a magazine for a pleasure boosting sex kit, she writes off for it. It duly arrives, and when she opens the box, she finds a list of instructions, two small bells and a tennis ball on a string. The instructions read : Place a bell on each nipple and suspend the tennis ball from your neck so it hangs at groin level - then, ring the bell, ring the bell, bounce the ball twice, ring the bell, ring...... If you find this works you might like to send off for our advanced kit. The woman practiced the movements, and finding that she and her husband are obtaining much more enjoyment from their sexual encounters, she sends off for the advanced kit. The new kit contained the same objects as the first one, but in addition a small blackboard and piece of chalk. The instructions read: Place a bell on each nipple and suspend the tennis ball from your neck so it hangs at groin level and put the piece of chalk between your buttocks. Ring the bell, ring the bell, bounce the ball twice, ring the bell, ring the bell, bounce the ball twice, then write 39 C(ents) on the blackboard !

One can almost feel the movement of the pelvis - the brain conjures up memories of such movements and you relive the experience of a very exciting and private moment in the presence of other individuals.

Joke humor was chosen to illustrate why and how conflict constitutes the central aspect of laughter evoking events because jokes comprise a relatively consistently structured, well defined grouping under the umbrella term "humor". As laughter is evoked by the same mechanisms in non-joke, non-verbal and unintentional humor as in joke humor, little would be gained from a lengthy discussion of these sub-divisions in the context of this essay, and a lack of such discussion should not be taken as an indication of their scope and importance. I have, however, included the example below as it connects, in a simple and direct manner, verbal and non-verbal humor.

The close relationship between men and dogs is so conceptually and emotively embedded in the human psyche it has not only given rise to the assumption that a man chooses an animal best suited to his personality, but also spawned such sayings as "every man and his dog", and led to the absurd idea that men come to look like their canine companions. The latter observation is interesting as it demonstrates the application of a psychological bias that leads to an active searching for commonality between two entities that are so closely associated that they are seen as a unity. The sight of an exceptionally large man walking a Chihuahua, or a very small man walking a Great Dane, cannot help but induce laughter in observers. The sight of the man and his "inappropriate" dog places within a single picture a contrast that violates all the conceptions and emotions that make us view a man and his dog as a unity. Comparing this real, non-verbal, humorous event to the processing of jokes, we can view the dog and its owner as the conflicting aspects induced by the joke mechanism within in the picture of a single coherent storyline. Both the man/dog observation and the processing of jokes result in the brain being presented with conflict within unity.

In regards to other non-joke material, there is a short reference to physical humor (slapstick) in the section "The role of empathy in humorous events" below.

Repression laughter                                                                                                                                                                                                There is another type of laughter event that might be placed in the "humor box" - although its source and the systems that mediate it are not the same as those for joke laughter - and this is repression laughter. There is conflict at every level of our being and none more important than our attempts to maintain our cultural cognitive norms in the face of reality. In his book, The Denial of Death (176-178), Ernest Becker quotes Otto Rank, a contemporary of Freud.

"If man is the more normal, healthy and happy the more he can... successfully... repress, displace, deny, rationalise, dramatise himself and deceive others, then it follows that the suffering of the neurotic comes....from painful truth."

Adding later: "......the essence of normality is the refusal of reality."

A large number of suicides, and admissions to psychiatric hospitals, attest to the fact that people often lose faith in the emotively maintained, collective, cognitive norms that direct our lives as cultural beings. Man is a risky biological experiment as the complex brain that keeps the species in existence can also reject the cultural constructs that are so essential for relatively fear-free mental stability, turn on its own organism, and eliminate it. The safeguard against destructive ways of thinking that operates relatively successfully in most people is repression. People do not necessarily commit suicide or become mentally ill because they are prone to thinking in a negative manner, but all thoughts that tend to depress militate against the attainment of good mental and physical health.

If someone bursts into laughter we can be fairly sure that it is a result of neural activity being opposed or denied expression in some way. In the case of repression, it is painful memories and tabooed ideas that are being denied access to consciousness: an idea that parallels Freud's concepts concerning dream and joke function (Freud 1905). We do not require jokes or staged situations to make us laugh; our most profound thoughts and anxieties can suddenly be disturbed by a simple everyday event forming the basis for a laughter inducing situation. The following is an example of repression laughter.

This real situation involves a burly, go-getting individual whose favorite saying was, "There are fish and leeches in the world, and God!, I hate being leeched!". He was observed at the breakfast table with a pencil in his hand on which a beetle was clambering. He tilted the pencil up and the beetle climbed to the top. He then turned the pencil upside-down, and the beetle turned and climbed to the top again. This was repeated many times and the individual laughed heartily throughout the exercise.

What should we make of this scene? There was more to it than him merely laughing at the stupidity of the beetle. Perhaps in a world in which we are all, to a great extent, controlled by external forces he unconsciously recognized a parallel between himself and the beetle. The repetitive nature of the beetle’s behavior suggested a further parallel. Most of us, at some time, have viewed our lives as a Sisyphean task, we seem to be going nowhere, other than in circles - getting up in the morning, going to work, going to bed, getting up in the morning......The beetle on the pencil had acted as a visual metaphor that evoked thoughts the man was reluctant to face. It would be dangerous to our mental stability if we constantly viewed life in a negative way, and the laughter process reduces the occurrence of such thoughts entering consciousness.

It is important to our survival that we remember traumatic events and attempt to avoid the situations which led to their occurrence. It is also important that the memories of traumatic experiences do not enter consciousness so often they disrupt our lives by imposing a constant state of anxiety. During the rapid memory search which occurs when the brain is processing humorous material, or during events of the kind described above, past traumas may form part of the network of associations that is induced. Laugher prevents the memories of highly emotive events from entering in to consciousness. It is possible that the unconscious inducement of a memory of a traumatic event, during a process which is voiding emotion, rather than registering it, may, in the same way as crying, bleed the memory of some of its emotive impact and reduce the tendency for  it to enter consciousness. The modern practice of encouraging patients to joke about their illnesses, and so lessen the impact of anxiety, is an excellent example of laughter aiding a return to a healthy mental equilibrium. In this case there is a conscious appreciation of the facts, but, as before, the thoughts, rather than being attended by a build up of emotion, are bound up in a process that is displacing it.

Tickling
A discussion of laughter would not be complete without an examination of the laughter inducing phenomenon we call tickling. If we cannot induce laughter by tickling ourselves it is obvious that laughter is a response to being touched by someone or something else. It would be quite disruptive if every time our hands accidentally brushed our bodies we drew back in fright and
we have enough body maps in the brain (both in the cortex and cerebellum) to tell us when two parts of our body are in contact, and such contacts are ignored. We can also detect the difference between touching and being touched - the difference between moving part of our bodies on a foreign object and foreign objects moving on our bodies. Anything moving on our bodies is probably alive and thus a potential danger. One only has to have an insect running about under the bed sheets to know how quickly and emotively we react to being touched in a certain way.

Not everyone is ticklish, but those who are have little conscious control over their reaction to being tickled. Laughter induced by tickling is indicative of a conflict between our emotive system, which is sending out danger signals, and our appreciation that no threat to our organism exists.

The fact that being tickled on the bottom of the feet and the ribs elicits the most vigorous response suggests that these areas were particularly vulnerable in our primate ancestors. A rapid withdrawal of the foot from an unseen, sharp object, or an animal, on the ground would minimise damage or the effect of a sting or bite. The fear reaction of all primates to snakes, and their specific warning calls that signal a snake's presence, suggests a long history of primate predation by large snakes (Isbell, L.2006). Sleeping primates are particularly vulnerable to large, night hunting, constrictor snakes, and as constrictors target the chest area to prevent their prey breathing, a rapid reflex response to being touched in this area would have been of significant survival value to our ape ancestors.

The role of empathy in humorous events                                                                                                                                                        Empathy, in the context of humorous events, fits into the general category of non-actionable emotive states. At times we feel strong emotions that cannot be immediately and appropriately expressed because the causes may be distant in time or space, or we are subject to various physical or mental constraints. Emotive responses to reported events and thinking about the past or contemplating the future, and the inhibition of physical activity when such activity would be self injurious or socially unacceptable, are examples where emotive states are not appropriately actionable. These situations often give rise to an act of displacement. In a classic example, the Greeks crudely solved the problem of the complex and troubled relationship between language, reality, emotion and action when, after a reported distant defeat, they displaced non-actionable anger into the inappropriate killing of the messenger. It should be noted here that the type of displacement in this Greek example is a psychological rather than a neurological phenomenon as the recipient of the message is expressing the engendered emotion, which in this case is anger. The displacement is from a potential target to an inappropriate target. Laughter displacement is of the kind defined in the introduction to this essay, where emotive activity is displaced in the brain and is expressed as a benign and inappropriate response.

In recent times - possibly due to the dissemination of psychological principles to those in service industries - in many peoples minds, the word "empathy" has become synonymous with, or at least inseparable from, the concept of sympathy. In the 1987 edition of The Oxford Companion To The Mind, empathy is discussed without any reference to human relationships at all and emphasizes our ability to associate ourselves with the inanimate. By comparing ourselves with, and to, everything we encounter, empathy aids us in measuring our strengths and weaknesses and determining appropriate physical and mental responses to specific situations. Empathy is particularly important in human interactions as we cannot have sympathy without empathy, although it should be noted that sympathy is not an automatic result of an empathetic state of mind.

Empathy is important in the processing of humorous situations as it is instrumental in the production of a changing complex of emotive responses as the event proceeds. When we observe another human being in extreme circumstances, or indulging in some form of extreme behaviour, there is an empathetic induction of an emotive state that is not personally and appropriately actionable (we do not take an analgesic because we "feel" another person's pain). This empathetic appreciation of a situation is particularly essential in non-verbal humorous events such as clowning and slapstick. When we see a man slip on a banana skin our mirror neurons, that map the movement and are probably also at the heart of our ability to empathize(Schulte-Rüther2007), evoke an immediate emotive state that is neither truly our own nor appropriately actionable. However, empathy may immediately give way to sympathy, which can give rise to appropriate action, such as helping the man to his feet and asking if he is hurt. Most people would not laugh if the fall was accompanied by a sickening thud as the man’s head hit the pavement, as this would immediately induce a sympathetic state of mind. Laughter, as a form of displacement, for all but the sadistic, will only occur if the fall is perceived to have caused no serious harm.

A common explanation for laughter evoked by the misfortune of others is that we laugh because it has not happened to us. This is correct, but for the wrong reasons, as it is not a matter of being pleased that we have escaped an embarrassing or painful experience. The fact that the slipping on a banana skin has not happened to us means the empathetically simulated emotive states of startle, fear and pain, are at odds with the reality of our position in the situation, and when not overridden by sympathy, this emotive activity is displaced into laughter.

The neuropsychology and neurophysiology of stress, displacement and laughter                                                                                          The reaction of a individual to a specific joke is determined by genetic and environmental/cultural factors. The material at which we laugh also changes with age; sexual jokes changing from toilet and genital humor, through sexual act humor, to jokes that incorporate sex and relationships. Young children enjoy word-play humor as they are still in the process of mastering language, but, for obvious reasons, cannot appreciate jokes that incorporate complex concepts.

Other than the rare sexual joke that has no internal mechanism, and relies on other factors to induce laughter, the effectiveness of a joke, appropriate to a given listener, is a function of the mechanism and all the associations and attendant emotions the joke content has evoked. We can view a joke as a small bomb: the joke mechanism, which sets up conflict, is like the detonator, on its own, quite capable of causing a small explosion; the main body of the bomb being made up of the associations and attendant emotions the joke content has evoked. The joke mechanism creates the brain state that facilitates the discharge of this neural activity.

If laughter is a form of displacement activity then conflict and displacement take place on an emotive level. Emotive weight is the degree of emotive activity available for displacement during the laughter process. Emotive weight can be viewed as arising from three main sources.

1) Emotive activity directly engendered by the joke content. (sexual and violence jokes carry a high emotive weight.)

2) Emotive activity induced by associations and personal memories during the divergent phase of joke processing.

3) Emotive activity extant at the time of the telling of the joke.

Emotive activity that sustains general stress, the relaxation of defensive mechanisms when with friends and the effects of the relaxing atmosphere at recreational social events all present emotive activity for displacement by laughter. Alcohol, nitrous oxide and recreational drugs also promote laughter, possible because they lower the threshold for its triggering.(Provine 1996) Many jokes with an acceptable mechanism do not evoke laughter and this may be because a certain emotive weight is necessary before laughter takes place. The triggering of laughter can therefore be viewed as a function of both joke mechanism and emotive weight.

In the introduction to this essay, displacement activities were associated with the following four situations:

a) Motivational ambivalence

b) Anticipation of change in activity

c) Actual change in activity

d) Internal conflict

The functions of displacement activities have already been described as: lowering stress during motivational conflict and facilitating the voiding of persistent emotive brain states when rapidly changing stimuli have rendered them redundant. Laughter not only parallels displacement activities in being a very effective releaser of stress but occurs in all the circumstances described above.

a) Motivational ambivalence               Example: The laughter of a young child being tossed in the air.

b) Anticipation of change in activity. Example: The immediate laughter when a well known comedian appears on a stage.

c) Actual change in activity.                Example: Laughter of schoolchildren let out of class for playtime.

d) Internal conflict.                                Example: Laughing at jokes.                                                                                                                       

It should also be noted here that there are parallels between laughter and a phenomenon already accepted as a displacement activity, yawning. (Schniter, 2001) The contagious aspect of laughter and yawning suggests that earlier in our evolutionary development both acted to coordinate and modulate group behavior

The neurophysiological effects of a bout of laughter reveal it as an evolutionary extension of a basic vocal, "fight or flight", displacement activity. Both a laughter inducing event and a "fight or flight" situation result in a stimulation of the immune system, which is a response to both physical and psychological stress. During an episode of acute stress our bodies are readied to deal with any insult ensuing from the difficult circumstances in which we find ourselves - this includes the activation and release of large numbers of immune cells into the blood. Laughter has been reported to increase the numbers of natural killer and activated T cells, along with an increase in concentrations of immunoglobulins and gama interferon which help to fight infection and activate immune cells. (Berk and Tan 1996)

Why should the telling of a joke, often in a relaxed atmosphere, lead to an immune response typical of a stress situation? The answer is that the processing conflict imposed by the joke mechanism mimics the motivational conflict typical of a "fight or flight" situation and leads to a similar response. The relationship between the nervous and immune systems is complex, as is the relationship between the immune system and neurotransmitters (Segerstrom and Miller 2004). The immune system can be directly stimulated by sympathetic nerve fibres from the brain as well as indirectly through stress hormones, and endogenous opioids can stimulate or inhibit the immune system, depending on their levels in the blood. Beta-endorphin is to be found in the neurons of both the central and peripheral nervous system and in the blood and lymphatic system. Some leukocytes (white blood cells) can produce beta-endorphin, secrete beta-endorphin and take up beta-endorphin from the blood (Csaba et al 2002) , and to further complicate the situation, at any given time, there is no correlation between the levels of endorphin in the circulatory system and those in the brain as water soluble peptides cannot pass through the blood-brain barrier.

It is this complexity that has made the endorphin/laughter connection so controversial. Although the production of beta- endorphin during a laughter evoking episode has been reported in many articles in the popular press no scientific research has confirmed that this is the case. A similar controversy surrounded the endorphin induced "runner's high" when the exposition of the blood-brain barrier findings brought into question the assumed connection between endorphin levels in the blood and the elevation of mood after strenuous exercise. However, recent advances in imaging techniques have enabled researchers to demonstrate an increase in opioids in the brain after strenuous exercise(Boecker et al 2008), and there is no reason to dismiss the idea that a similar increase in the brain's opioids will be found after a laughter evoking event. Studies into the connection between the processing of humorous events and what is termed "reward" suggests that this might be the case (Mobbs 2003), although it is possible that the systems being investigated in these studies are concerned more with a motivation (wanting) than reward (liking).

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