Laughter and humour

Humor, displacement activities and constrictor snakes: the laughter connection 

I posit that the most fruitful way to shed light on the nature of what we have termed "humor" is to apply a bottom-up hypothesis rather than applying a top-down approach, typical of cognitive/linguistic theories. I propose that the laughter process, set in train by both verbal and non-verbal events, can be traced upwards from its neurological origins to its behavioral expression, in the short term, and allows for a plausible explanation of its evolutionary history in the long term. 

I consider that many of the problems encountered when attempting to explain the nature of humor are semantic in nature, and even before we begin a study of the topic, our assumption that we know what the word "humour" means, biases our understanding.. Even authorities on the topic sometimes write nonsensical phrases such as, "humor takes place" or "we experience humor" These statements are nonsensical because humor is a mental construct, a categorical concept (as is furniture) Below is a quote from  Médéric Gasquet-Cyrus on this subject: 

"Of course, saying that "humor doesn't exist" is a methodological point of view ; we must prove the occurrences of humor, each time it appears. I think that many scholars have made a confusion between the word "humor" and the wide range of events occurring in everyday life, in literature, in arts, etc., labelled "humor" by human beings. Of course, "humor exists"... but is there only one way to define it, to define its mechanisms ?... I'm not sure of this. As we all know here, all the definitions proposed by all scholars (from Antiquity to nowadays) don't explain the phenomenon at a moment or another. Because there is no ONE essence of the phenomenon nor ONE definition which explains it ." Médéric Gasquet-Cyrus (University of Aix-Marseille/France) 

I suggest that the word "humor" should only be used to denote a general area of study and never in a descriptive manner as its application lacks the rigor demanded of scientific usage. Within the general study of humor, laughter evoking events are the only forms that can be clearly defined beyond their cultural meanings, and the only forms whose processing progress can be mapped, to any degree, from their neural substrates through to their socio-behavioral effects. Different researchers have approached what they view as humor from different points of view, producing mainly, top-down theories which stand in isolation from each other and so hinder any fruitful debate from taking place. 

I counter the criticism that my hypothesis is a reductionist theory of laughter rather than a theory of a particular type of what we have termed “humor”. I propose that an exposition of the nature of laughter will also explain how, and why, the syntactic and semantic aspects of the joke story, and the juxtaposing of conflicting thoughts and emotions in non-verbal situations, lead to its evocation. (disinhibition, in neurological terms) 

“Much time and effort has been spent in attempts to define humor and fashion humor theories. Most researchers now accept that there can be no definitive exposition of the nature of humor, but there is still much disagreement when it comes to theories. When considering the nature of jokes and laughter evoking situations, the space/time frame that should be applied extends further than the functioning of the individual’s brain that is processing them. The individual might comment that a joke made him laugh - the joke was the cause of the laughter - the joke preceded the laughter - but when we enlarge the space/time frame and consider the evolution of the systems in his brain that process the jokes, then the picture changes. We would not tell jokes if they did not give rise to laughter and a feeling we describe as pleasurable, which has been shown to accompany a decrease in stress levels and muscle tension. In fact, the word "joke" would not exist, as we distinguish the joke from a statement, story, puzzle or piece of nonsense, not only by the context in which it is delivered, but by its bodily effects. The laughter process preceded language in our evolution and so we can say it is the laughter process that is the cause of the joke, in so far as the existence of the joke is dependent on the existence of the laughter process and its general form predetermined by the laughter process.” 

Humor theories
I favour the incongruity theory but prefers the use of the term “conflicting” rather than “incongruous” as “conflicting” is not as restrictive as “incongruous” when discussing humor and laughter outside a linguistic context. My ideas could be termed an “unresolved conflict” theory.  Although I agree that conflict is at the heart of laughter evoking events, I believes it is irresolvable conflict that induces laughter. The early, strict linguistic/cognitive theory of “humor” separated the processing of verbal, laughter evoking events and laughter itself, and left the impression that laughter was a subsequential rather than consequential response - a response to a pleasure inducing outcome rather than a response elicited during the processing of the laughter evoking event. The early, strict cognitive/ linguistic theory parading a reasoned, post-joke analysis of the mechanism and an unsubstantiated “getting” of the joke as the actual neurological processing , calling it “resolution”. The theory takes little note of the emotional aspects of humorous event processing, and ignores the fact that although the cognitive conflicts may be understood (resolved, as the theory’s proponents see it), the conflicting cognitive and emotive contexts cannot be reconciled.   

Berlyne's “arousal jag” theory of humor appears to have been disproved by the work of Schachter and Wheeler, although, as I point out, emotional arousal, that I term “emotive weight” does fuel laughter during its evocation. Hence the evocation of mirthful laughter can be viewed as a function of both joke mechanism and emotive weight. Young children enjoy simple punning jokes as they are still struggling with language, but for adults there is not enough emotive weight engendered by simple puns for the mechanism (two words sounding the same, but with different meanings) to give rise to mirthful laughter. 

A joke has a theme, a story line/content, and a mechanism. The theme can be anything at all, and although some themes do not affect the volume and duration of the evoked laughter, others do, due to their emotive nature. The content is everything done and said in the story. Again, if the content is of an emotive nature, it will affect the quality of the laughter. Finally, the mechanism is a juxtaposing of conflicting cognitive, and or, emotive aspects of the joke content. 

When analysing the processing of jokes, I came to realize that only one of the three main “humor” theories (aggression, incongruity and relief) incongruity (conflict), constituted a true theory. The other two 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 pace during the telling of a joke:

Aggression can be a motivation to express feelings in the form of jokes, and when embedded in the content of the joke, in the same manner as sexual, political and religious content, it adds emotive weight
The relief theory is a "why" rather than a "how" theory. A feeling of relief/ pleasure is merely an effect of the joke processing. 

Incongruity (“conflict" in my parlance) is seen as central to laughter evoking humor, and when viewed as an incongruity unresolved theory, I consider it the only theory that adequately explains the psychological, physiological and neurological aspects of laughter evoking events and also allows for the placement of laughter in a plausible evolutionary context.

Some physiological effects of laughter evoking events

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) In an earlier paper Berk reports a decrease in the blood levels of epinephrine (often called the fight or flight hormone) as a result of mirthful laughter, although in the majority of experiments dealing with the neurophysiological effects of laughter an increase in stress hormones has been detected. Indeed, the reported levels of cytotoxic cells, neuro-immunologically active molecules and stress hormones in the blood vary so much from experiment to experiment that no specific conclusions can be made that are pertinent to the present thesis. Although we will have to wait until the inherent flaws in the various approaches are addressed, we can come to a general conclusion: however muted and variable the neurophysiological effects of laughter are, they do parallel those typical of a response to a stressful event. Why should the telling of a joke, often in a relaxed atmosphere, lead to an immune response typical of a stress situation?  

Stress and laughter

None of the popular humor theories answer the following questions. What is the true nature of laughter ? What are the mental processes that lead to its evocation? If we "get" jokes, why do we laugh at all?
The simplistic answer to the last question is that when we have "gotten" the joke we are pleased and so we laugh. I view this answer to be erroneous on two counts. Firstly, it places the conscious, cultural self, within the unconscious processing that takes place when we listen to jokes or find ourselves in laughter evoking situations. And, secondly, it infers that we laugh because we feel pleasure rather than, as I posit, we feel pleasure because we laugh. I believe that the laughter process is instrumental in the lowering of stress, making the pleasure derived from laughter a negative form of pleasure, and bringing into question its nature in other situations.

I saw that the quadrant of mood ((After Cox and Griffiths 1995) suggests that pleasure is associated with the lowering of stress, and mental pain with the increasing of stress, depending on arousal levels.

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 fear response which is quickly opposed by the knowledge/faith that they are in no danger; as when they are being chased or tossed about by someone they trust. A feeling of mirth can be viewed as the conscious appreciation of the arousal effects of fear in its absence.  

With this in mind, and being trained in the biological sciences, I noticed a parallel between the conflicting cognitions and emotions found in jokes and the conflicting motivations that occur in fight or flight situations in both humans and animals. When, for various reasons, animals find themselves in situations where fight or flight is impossible, or the outcome of either action is uncertain, they automatically fall into benign behaviours that seemingly bear very little relationship to the original situation. These behaviors are called displacement activities. Fighting male birds, for example, may peck at grass, or preen, when uncertain whether to attack or flee from an opponent; similarly, a human may scratch his or her head when they do not know which of two options to choose. I came to the conclusion that laughter was an exapted form of a displacement activity. 

There have been some objections to the use of the phrase "displacement activity" as it is often applied to two different phenomena. One is described above, the other is humorously termed " Kick the cat syndrome" - a classic example being the ancient Greeks habit of killing the bringer of bad news. After a reported distant defeat, they inappropriately vented their anger by killing 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 shift being from a potential target to an inappropriate target. Laughter displacement behavior is of the kind defined above; where the shift takes place in the brain and is often expressed as a benign, seemingly inappropriate response.. 

    I put forward the following in defence of my displacement theory:                                                                    

 In the paper, Displacement Activities as a Behavioral Measure of Stress in Nonhuman Primates and Human Subjects, Alfonso Troisi concludes that displacement behavior is a valid measure of stress in nonhuman primates and human subjects - the greater the stress the more primates exhibit displacement behaviours. Human displacement behaviors result in the lowering of stress, and a concomitant loss of muscle tone, a typical effect of a laughter evoking event.

The situations that give rise to displacement behaviors in human beings -and in other animals- are according to Schniter   (2001), change, or anticipation of change, in activity, internal conflict, or motivational ambivalence. Laughing fits particularly neatly within these criteria.  


Although many areas of the brain that are implicated in laughter evocation are also concerned with the detection of error and conflict, it is not clear how many of these areas are directly responsible for disinhibiting displacement activities. Very few experiments have been performed to clarify this issue. However, in 1980, Robbins and Koob found that displacement drinking in rats, that were denied access to food for a short period, was attenuated by lesions of the mesolimbic dopamine system, an area Sokichi Sakuragi sees as important in the generation of mirthful laughter. One mediating aspect of mood appears to be the balance between the neural transmitters, dopamine and serotonin. These neurotransmitters are also important in avoidance and approach behaviors as well as those of fight and flight. Displacement activities are interventions of often benign behaviors that temporarily shut down any possibility of extreme action taking place, as seen in the example of fighting male birds. Dopamine can be viewed as the “go” neuro transmitter and serotonin the “whoa” neurotransmitter. The attenuation of the rat’s displacement drinking probably occurred because, by lowering dopamine levels, the areas of the brain responsible for the "wanting" response (as Kent Berridge views it) was no longer being stimulated.                                 

There are parallels between laughter and a phenomenon already accepted as a displacement activity, that of yawning. (Schniter 2001) The contagious aspect of laughter and yawning suggests that earlier in our evolutionary development both could have acted to coordinate and modulate group behaviour. Laughing and yawning can take place in response to similar situations. One situation, that I personally witnessed, occurred when a student, while waiting to enter an examination room, burst into uncontrollable laughter at a very weak joke someone made. Paratroopers have been known to yawn while waiting to jump out of a plane, and athletes sometimes yawn when they are waiting for the start of a race,

However, Delius proposes that displacement activities take place in three distinct situations : motivational conflict, frustration of consummatory acts and physical thwarting of performance, The example of student laughter was a response to fear/anxiety, but there is a probability that the yawning of both paratroopers and athletes, primed for action, was a response to the thwarting of action due to the delay. Obedient dogs sometimes yawn when they are forbidden to indulge in their favourite activities, and children cry when they are stopped from doing things that they enjoy. I view crying as another displacement activity, but the cause of its disinhibition is closer in nature to that of yawning than to laughter. Although yawning serves different functions in different animals, both crying and yawning can be viewed as displacement behaviours that are disinhibited when actions are opposed. 

Laughter as an exapted displacement activity

Some displacement activities intervene when an animal is uncertain of the outcome of its actions, often  in life threatening situations. In the fighting birds example, the displacement activities are easily recognised as "normal" behaviors taking place in unusual circumstances, but the origins of laughter and yawning are more difficult to discern. Laughter has an accepted history going back as far as the common ancestor of the apes and humans. Some believe that yawning is common to all vertebrate groups, and although, at present, there is no evidence that all behaviors considered to be yawning are homologous, I propose that laughter has a longer history than has been assumed.

Exaptation is
a shift in the function of a trait during evolution. One example is the feather, which is thought to have evolved as insulation and was exapted for flight. Not all exaptations are of a physical nature, and it has been suggested  that neural programs that are necessary for the sequencing of movements and navigation could function as a deep structure for language.
 In an extract from my unpublished essay: Laughter as an exapted displacement activity: the implications for humor theory. I write:

"I have spent some time in this essay musing on the nature of language. I believe this was important, not only because many mirthful laughter eliciting events are verbal in nature, but to highlight the fact that although the laughter displacement activity can be disinhibited during the processing of language (jokes), in the rest of the vertebrates displacement activities are associated with action rather than thought. However, this is not so surprising when it is realized that language does not depend on evolutionary new, "clip on" systems but is rooted in the oldest systems that mediate motivation and action. Language sits on the top of a series of exapations, from the reorganization of reactive systems in the development of cognition ( Holk Cruse 2003) to the exaptation of primate vocalization in the service of speech. Language probably shares many systems that evolved to manage our dealings with the physical world. William Calvin, (Calvin 1993) proposes that the sequencing of movements (as in throwing) and the sequencing within language are mediated by the same systems and it is possible that the hippocampus is not only important to the physical act of navigation but also "navigates" the form and content of written and spoken language. (O’Keefe and Nadel 1978)" 

It is not a giant leap from these ideas to the realization that the fight or flight conflict during real life situations could be  mirrored in the cognitive and emotive conflicts induced by joke mechanisms, and laughter represents a type of intervention that prey animals utilize when fight or flight are not possible options. Laughter would seem to be of little value as a form of defence, but when it is realized that what we now term "laughter" is an unvoiced rapid panting in our closest relatives the chimpanzees, the possibility arises that laugher could be an respiratory adaptation of one aspect of a defence strategy.

Displacement activities are sometimes described as merely "going through the motions". They appear to lack the autonomic arousal that accompanies the original behaviours.
Bernd Heinrich describes how cranes, disturbed by the presence of a dead horse, responded by slipping into "a displacement behaviour of going through some motions reminiscent of nest building". I consider  the mystery surrounding the origins of both laughing and yawning arises because they are truncated displacement activities based on ancient behaviours that are no longer in our repertoire of responses. The origin of yawning remains a mystery, but under certain conditions a prime candidate for the behaviour, that is now represented by laughter, known as the vigilance reaction, is reactivated.

Laughter, cataplexy and the vigilance reaction
Narcolepsy is a sleep disorder where the affected individual falls asleep without warning. Narcolepsy is usually, but not always, accompanied by cataplexy, which is characterised by sudden physical collapse associated with strong emotions or laughter. It has been suggested that cataplexy is an expression of an ancestral reaction to fear (emotion). (Vincezo Donadio et al)

What is interesting about cataplexy is the fact that it is almost identical to what is known as the vigilance reaction, in which an animal loses muscle tone (atonia) stops breathing after an inhalation (inspiratory apnea) has a drop in heartrate (bradycardia) and an increase in blood pressure (pressor response), and yet is conscious and alert.

In experiments with rabbits, it has been found that the vigilance reaction can be separately elicited by electrical stimulation of specific sites of two areas of the brain - the periaqueductal grey matter (PGA) and the hypothalamus. (Duan et al 1997) It was discovered that when certain nerves from the PGA to the hypothalamus were severed, the hypothalamic vigilance reaction was unaffected, suggesting that the periaqueductal grey area was not essential for the elicitation of the full-blown vigilance reaction.

In the same paper it was suggested that the physical and autonomic components of the vigilance response were neuroanatomically partitioned. The striated respiratory muscles are stimulated by the somatic nervous system and do not require autonomic input to function. The partitioning of the physical and autonomic system innervation heightens the possibility that laughter originated as a truncated expression of the vigilance reaction, in which all the other aspects of the phenomenon under autonomic mediation were not represented.

Laughter in humans and chimpanzees, and the vigilance reaction in rabbits.

I posit that the laughter response was exapted more than once in the history of the line of apes that led to the existence of the Homo group. Life for the hominids, out in the grasslands, required different strategies to those employed in a forest environment. 

  "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, an audible and contagious displacement activity would have been particularly effective in calming the members of the band and preventing panic scattering" 

The laughter typical of chimpanzees is not fully voiced, and takes the form of rapid panting. Also, in rabbits, the inspiratory apnea of the vigilance reaction sometimes gives way to panting (tachypnea). It is possible, that in the line of apes that led to modern humans, rapid panting gained a loud vocal component, and acted as a means of communication.  Ramachandran 1998).

I believe that a second exaptation took place with the advent of language.

"It is possible that the disinhibition of the vigilance reaction during in the fight or flight conflicts in the physical reality of early mammalian life is paralleled by the intervention of laughter in the emotive and cognitive conflicts of human mental life."

"Playing dead" and the vigilance response

The predator - prey evolutionary arms race has been taking place for millions of years. Some prey animals have become exceptionally fast runners and their young escape detection by having camouflage colouring, hiding and becoming immobile when a predator is detected. In the presence of a predator, some prey animals employ a passive form of defence. The classic example is the North American opossum that, when threatened, falls unconscious in a state of tonic immobility and secretes a foul smelling fluid from anal glands.

I consider the atavistic vigilance reaction to be a particularly strange defence response. Which prey animal had it initially evolved to counter, and why had it become redundant?

There was only one type of predator that could account for the particular behavioural, cardiorespiratory and muscular responses that characterize the vigilance reaction: constrictor snakes.

1) Inspirational apnoea / tachypnoea
Constrictor snakes tighten their coils during the inhalation phase of the prey's respiration. By holding its breath, a prey animal could slow down constriction and even the rapidity of tachypnoea, in which the respiration is mainly diaphragmatic with little chest deformation, could have disrupted a snake's timing during constriction.

2) Bradycardia                                                                                                                                  
Constrictor snakes respond to the prey's heartbeat. The higher the heartrate the tighter the snake's constrictions.

3) Pressor response
A high blood pressure would prime the prey animal for action and initially resist the snake's constrictions.

4) Atonia                                                                                                                                            
Struggling stimulates snakes to increase constriction.

5) Consciousness and alertness                                                                                                                 Unlike the unconscious opossum, the prey animal could take advantage of the slowing and disruption of the snake's constrictions, and perhaps escape.

It is possible that the small mammals were heavily predated by constrictor snakes early in their evolution and the vigilance reaction gave them a better chance of surviving a snake attack.
If this is the case, and if the joke mechanism reflects the fight or flight conflict in real life situations, then laughter is an exapted displacement activity and the joke has possibly been 50 million years in the making.