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| Acknowledgments | p. ix |
| Introduction | p. xi |
| Human Behavior | |
| I Just Had to Laugh | p. 3 |
| Seeing Things | p. 18 |
| Sane in an Insane World | p. 27 |
| The Barmaid's Brain | p. 40 |
| Curiosities of Life | |
| The Invention of Thievery | p. 55 |
| The Plant That Rolls | p. 67 |
| Consumed by Learning | p. 77 |
| Why Do Moths Fly to Lights? | p. 87 |
| Homo Aquaticus | p. 102 |
| Science and History | |
| Saint Joan | p. 121 |
| The Effect of Witchcraft on the Brain | p. 138 |
| The Vinland Map | p. 150 |
| The Burning Mirrors of Syracuse | p. 165 |
| The Monks Who Saw the Moon Split Open | p. 174 |
| Natural Battles | |
| Antlion King | p. 187 |
| The Bacteria Eaters | p. 199 |
| An Uneasy Bargain | p. 210 |
| A Silver Lining | p. 222 |
| How Things Work | |
| Tee Time at the Royal Institution | p. 233 |
| It'll Practically Go Forever | p. 242 |
| Going Up? | p. 254 |
| Bibliography | p. 265 |
| Table of Contents provided by Syndetics. All Rights Reserved. |
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Chapter One
I Just Had to Laugh
* * *
There are few things as funny as reading psychologists' or doctors descriptions of laughter:
The primary component of laughter is an abrupt, strong expiration at the beginning, followed by a series of expiration-inspiration microcycles with interval pauses.
The true manifestation of laughter is ... the abrupt expiration due to a sudden contraction of the intercostal muscles.
A laugh is characterised by a series of short vowel-like notes (syllables), each about 75 milliseconds long ...
It's enough to set you off on a series of expiration-inspiration microcycles with interval pauses. But these techno-speak descriptions, as remote from reality as they seem, are the first step in defining, then trying to understand what laughter is and why we do it. The problem is that because we are so familiar with it (it has been claimed that there is no record of anyone who has not laughed at least once in his/her life), we overlook the fact that it is a peculiar habit and a fundamentally mysterious part of our behavior. As psychologist Robert Provine (who's one of the few academics to study laughter) wrote: "What would [an alien] make of the large bipedal animals emitting paroxysms of sound from a toothy vent in their faces?"
When Provine performed some detailed acoustic studies of laughter, he uncovered some unexpected links to speech. He took recorded samples of laughter to the National Zoo in Washington, DC, where they were analyzed with a sound spectrograph, which produces images of the frequency and intensity of animal vocalizations. The resulting data prompted Provine to describe laughter as a series of vowel-like sounds repeated at regular intervals: ha-ha-ha-ha. These are all about the same length. But the vowels themselves can change: ho-ho-ho-ho. Usually a person laughs roughly the same way all the time--I bet you could identify the laughter of your friends sight unseen, even if the pitch were altered. Provine pointed out something that might seem obvious but nonetheless needs to be said: two different laugh-vowel sounds are unlikely to appear together in the same laugh. Santa never laughs ho-ha-ho-ha. If there are intrusions of a different sound, they occur only at the beginning or the end of the laugh.
That's not all. These experiments also revealed that laugh notes, like the notes of the singing or speaking voice, consist of a fundamental frequency (or pitch) accompanied by a number of harmonics or multiples of that frequency. The fundamental frequency of male laughter is almost an octave below that of females; the female frequency is close to the C above middle C on the piano, while the male frequency is roughly the D next to middle C. Robert Provine argues that while there is tremendous variation within laughter, all human laughs follow this pattern.
Provine found that the spaces between the laugh vowels contribute very little to the sound: if they're removed, leaving only "has" and "ho's," the laugh still sounds almost exactly the same. The punctuating silences themselves, when strung together, amount to nothing more than a prolonged sigh. One final point from these sonic investigations: while the individual notes of laughter sound much the same played backwards or forwards, an entire sequence of backward laughter sounds weird because it rises in volume, instead of fading out as it does normally as we run out of breath.
Even given the relatively constant timing and sound qualities of laughter, there is obviously still room for tremendous variation. In response to a bad joke, you barely make it over the laughter threshold (although the social situation might demand that you laugh as best you can), but you can also "dissolve" into laughter so powerful it leaves you bent over and weeping.
The anatomy of laughter represents only one small part of the research on the subject. Social psychologists and psychiatrists have emptied a few inkwells with their speculations on the functions of laughter. Freud--naturally--weighed in with a theory that laughter represented a discharge of built-up sexual tension, and while there aren't many who agree with him about the sexual part, there is general agreement that laughter results from an abrupt change in the direction of thought or a sudden reduction in tension or both. A joke leads you along one path, often gravely serious, then suddenly reverses with the punchline. Slapstick juxtaposes a man in a suit with a cream pie in his face. The classic example of tension reduction is the movie portrayal of the mob boss and his boys sitting around the table. He smiles, they do the same. He laughs, they laugh. He stops, they stop. He laughs heartily, they fall all over themselves in hysterics.
There are entire books written about what triggers laughter and why; there is nothing dramatically new on that front. However, there has been research in recent years on the brain mechanisms underlying laughter and even some guesses as to how this unique behavior came to be.
Searching the brain for a "laugh center" isn't easy. Everybody laughs, so you can't compare laughers and non-laughers; brain imaging requires the person being imaged to stay relatively still, a great challenge when you're laughing. But in any kind of brain research there are individuals with some kind of brain damage that specifically affects the behavior you're looking for; in this case, the damage causes what's called "pathological laughter."
One of the most recent cases involved a twenty-three-year-old male ensign in the US Navy who was at the controls of a jet trainer when his instructor heard what he described as "uproarious" laughter. The aircraft began drifting toward another flying in the same formation and the instructor seized the controls to prevent a mid-air collision. The pilot was assumed to have a peculiar form of epilepsy and was sent to a neurologist.
The ensign explained that the symptoms had begun about eighteen months earlier: his family and friends started telling him that he was laughing in his sleep, sometimes so loudly he would wake himself up. What was worse, at least socially, was that he would begin laughing loudly at inappropriate times during the day, like at officers' meetings. Apparently these spells of laughter could happen at any time, and lasted about ten seconds. They were accompanied by a vague feeling of lost concentration; sometimes this feeling occurred without the laughter. After about ten seconds, he would snap out of the seizure and go on as before. Most significantly, the patient reported that his laughter was not accompanied by any feelings of mirth; in other words, the act of laughing was some sort of automatic act--a seizure--triggered independently of his thoughts and actions at the time.
The patient was put on an anti-seizure medication and apparently has never suffered a laugh attack since, although for some time he continued to experience the strange aura that accompanied the laughter. This case suggests strongly that there is some sort of laughter center in the brain, the activity of which was being triggered in these seizures. Although the patient once had a seizure while doctors were giving him an EEG, an electroencephalogram, it wasn't possible to pinpoint the location of any specific site that might have been involved.
Laughter seizures like this have been reported before but are rare: they represent less than 1 percent of all cases of epilepsy, and when taken together provide only a vague indication of which places in the brain might be involved in the generation or control of laughter. Most patients with these unusual seizures, like the laughing pilot, experience no joy or merriment with their laughter.
In another case, reported in 1990, an employee of a fast-food restaurant arrived at the emergency ward in Akron, Ohio, laughing uncontrollably. Apparently he had been spraying an insecticide when the wind changed and he inhaled a full breath of the compound WC Insect Finish. Within seconds he had started to laugh and couldn't stop. He felt some numbness and tremor but was otherwise completely normal. After an hour and forty minutes of laughter he began to complain of pain in his abdomen. When he was given a shot of Valium, the pain, tremor, and laughter stopped, never to reappear.
The most common causes of pathological laughter are brain diseases that eventually disrupt centers that control a variety of normal movements. So in some cases patients begin to lose control of their chewing, speaking, sometimes even breathing, but at the same time are capable of crying, swallowing, or laughing. Such patients may laugh either disproportionately loudly or at inappropriate times. Even the laughter itself can assume a disturbing quality: "prolonged and distorted like a scream or a wail."
There isn't much that can be said from these disparate cases other than there are likely multiple neural pathways governing laughter. Some must be inhibitory, and when those are damaged patients laugh loudly and inappropriately. Some are excitatory. When those pathways are triggered abnormally, as by an insecticide, laughing can't be turned off. But all of this is pretty vague--practically any human behavior involves inhibitory and excitatory pathways in the brain.
However, early in 1998 a case of laughter was reported that shed new light on what goes on in the laughing brain. A group of researchers at UCLA led by Dr. Itzhak Fried were exploring the brain of a sixteen-year-old girl who was suffering from intractable epileptic seizures. Their intent was to find the scarred or abnormal part of the brain that was triggering the girl's seizures, then remove it surgically. To do that they had exposed the surface of her brain and were stimulating a variety of places with an electrode--this kind of surface mapping has been standard pre-surgical practice since Wilder Penfield did it in the 1940s and 1950s. Just as Penfield might have reawakened long-lost memories with the tip of his electrode (although that claim is controversial), the UCLA team came up with their own surprise. Whenever they stimulated a part of the brain called the supplementary motor area, at the front of the brain, the girl laughed.
This was a curious finding for more than one reason. The supplementary motor area is a part of the brain that is a sophisticated neural add-on (at least in evolutionary terms) to the so-called primary motor cortex, a strip of tissue at the top of the brain that issues commands for movements. The supplementary motor area refines those movements by organizing, planning and helping to execute complicated sequences of them, such as playing the melody of a Bach fugue on the piano or uttering a complicated sentence. The laughter-sensitive area was close to the area responsible for speech, but it seems odd that this part of the brain should be recruited for the genesis of laughter when you consider that the sounds of laughter are not complicated, but in fact are relatively stereotyped and repetitive. Nonetheless, touching the electrode to this piece of brain that is only about one-third of a square inch invariably caused the girl to laugh.
But this finding wasn't as intriguing as the girl's reaction to her own laughter. Unlike patients who laugh because of brain damage, the girl at UCLA seemed to have the full laughter experience: she experienced mirth, and even more than that, claimed to be able to identify the "funny" event that caused her to laugh. So for instance, when she was looking at pictures to test her ability to name objects, and the electrode touched the laughter center, she exclaimed, "the horse is funny"; once she just looked at the doctors and said, "you guys are just so funny ... standing around." The only reasonable explanation for this strange labeling of unfunny events as laughter-provoking is that the girl's brain was making it all up, confabulating to explain (to itself) why there was laughter.
This isn't such an outrageous idea. Several years ago neuroscientist Michael Gazzaniga proposed that the left hemisphere of the brain contained something he called the "interpreter," a neural center whose job it is to make sense of activity in other parts of the brain. Gazzaniga was attempting to explain some of the weird moments he had witnessed when working with split-brain patients, people who have had the connection between their two hemispheres severed in order to limit the spread of seizures. Gazzaniga had often seen the left hemisphere fabricate explanations. For instance, the command, "walk," was given to a patient's right hemisphere--and that hemisphere only. When, moments later, the patient got up to "walk," the question, "What are you doing?" was directed to his left hemisphere. The left hemisphere, able to respond verbally because it contains the speech centers, produced the reply: "I'm thirsty, I just thought I'd go down the hall and get a Coke." First came the behavior, then the rationale.
So when the sixteen-year-old laughed, then remarked on how funny the assembled doctors were, her brain was apparently doing the same thing. The UCLA group suggests that a joke, the resulting feeling of mirth, and the act of laughter are all stations along a neural network in the brain. While normally the joke comes first, this case illustrates that it is possible to produce the laughter first, which then triggers the rest of the network. However, you have to be cautious here: when you consider the number of different situations that can provoke laughter, from tickling to jokes to nervousness, and the complexity of the muscle movements involved, there is no way that the brain pathways governing laughter can be anything less than extremely complicated.
The implications of the UCLA experiment are profound--especially for stand-up comics. If a comic can incite the people in the audience to laugh--for whatever reason--their brains will likely attribute that laughter to the comic's jokes. Canned laughter in television sitcoms has been used for nearly fifty years now and researchers have confirmed that it both makes viewers laugh more and persuades them that the show is funnier, two quite different conclusions. Robert Provine has suggested that our brains might contain laughter detectors that are linked more or less directly to laughter generators, so that hearing laughter would make us laugh, even in the absence of anything funny. But such a neural automatism wouldn't by itself convince viewers that laugh-tracked programs were actually funnier--that would only happen if there were additional brain mechanisms whose job it was to identify causes for that laughter. It appears from the UCLA experiment that such brain software does exist.
Laughter is contagious, but only to a point. I have seen claims that laughter by itself--accompanied by nothing that could be construed as a joke--does not provoke laughter in others, but there are recordings of both laughter alone, and laughter with music, that seem to have the effect of making the listeners laugh. On the other hand, Robert Provine found that if he played an eighteen-second recording of laughter over and over again for students, they laughed less and less in response, until by the tenth time almost no one laughed and most of them described the laughter as obnoxious. I'm sure the social psychology of laughter will turn out to be as complex as its brain mechanisms.
There is one example in the medical literature from 1963 of the contagiousness of laughter run amok. The report is titled An Epidemic of Laughing in the Bukoba District of Tanganyika . Hundreds of people, mostly adolescent girls (but also boys and adults of both sexes), succumbed to an apparent epidemic of laughter. It began in January 1962 in Kashasha village near Lake Victoria (in what is now Tanzania). Children would suddenly start laughing and crying, sometimes for hours at a time. There were no physical symptoms: no fever, no tremors, no fainting, and certainly no fatalities. The laughing attacks spread from one afflicted person to the next--at the mission school in Kashasha, 95 out of 159 pupils were affected over a period of about seven weeks. The school closed in March, and a few days later, the epidemic of laughter broke out in some of the villages to which the girls from the school had been transferred. It was clear that the laughter spread from person to person, but no evidence of any infectious agent, toxic substance in food, or physical abnormality in the patients was ever found. All laboratory searches for abnormalities in the blood such as viruses or bacteria came up empty and all the investigating doctors could conclude was that it was a case of mass hysteria. It still ranks as one of the most peculiar cases of pathological laughter and the most extreme demonstration of the contagiousness of laughter.
None of what we know about laughter, the multiple sites in the brain controlling it, its contagiousness, and its peculiar repetitive form tell us anything about why we do it. In that sense, although laughing is intimately bound up with conversation, it is more like crying (Why shed drops of water from your eyes to express emotion?) than speech.
There have been some attempts to explain why we laugh, as opposed to why we find something amusing. A better way to put it might be: Why do we respond to humor by emitting bursts of weird sounds? Nobody really knows of course, but there are some interesting speculations on the matter.
One that seems to come right out of left field has been proposed by Vilayanur Ramachandran of the University of California at San Diego. Left field in this instance is the unusual brain-damage syndrome called anosognosia, the lack of awareness or even denial of a body part. This is sometimes seen in patients who have recently suffered a stroke that has paralyzed one side of the body. I related the details of one such case in The Burning House: a woman had suffered a stroke that paralyzed her left side, and while in the hospital came to believe that the left arm that was clearly attached to her body was not actually hers. She believed--honestly and completely--that it had been the left arm of the person who had occupied her bed before her. She was able to back up this belief by pointing out details that proved to her it wasn't her arm, such as the hospital bracelet with a name different from hers by one letter (apparently she was misreading it), thicker fingers on her hand, and a wedding band that seemed like hers but different in detail.
Vilayanur Ramachandran begins his theory of laughter by detailing several cases like this, some of which involved simple denial that paralysis existed:
"Can you point to my nose with your right hand?"
(The patient points)
"Mrs. D, point to me with your left hand."
(Her hand lies paralyzed in front of her.)
"Mrs. D, are you pointing to my nose?"
"Yes."
"Can you clearly see it pointing?"
"Yes, it is about two inches from your nose."
It might seem obvious that such patients are simply protecting themselves from the awful reality of what has happened (and in the case I cited the patient eventually came to understand that it was indeed her arm), but Ramachandran points out that it never seems to happen when the damage occurs to the left hemisphere of the brain (thus paralyzing the right side of the body). Anosognosia appears when the right hemisphere is damaged and the left is intact. And it is that hemispheric difference that Ramachandran thinks is the key to both this syndrome and laughter.
He argues that the left hemisphere has the responsibility for maintaining a thread of consistency in our behavior, connecting moment-by-moment experiences in a sensible way. This is an important role because among the thousands of sensory impressions gaining access to our brains are some that don't fit with your concept of the world and your place in it. It's the job of your left hemisphere to screen those out and maintain what Ramachandran calls "the script." The right hemisphere, on the other hand, has the opposite role: when some important new piece of information comes along, it is the job of the right hemisphere to persuade the left that this information, rather than being disregarded, should be incorporated into the brain's script. Ramachandran thinks of the right hemisphere as the devil's advocate. The role he assigns to the left hemisphere is reminiscent of Michael Gazzaniga's left-brain interpreter.
In anosognosia, the right hemisphere--the devil's advocate--has been disabled, and the left hemisphere is now free to go to the most absurd lengths to cling to the script. It will ignore even the most dramatic anomalies. It will not even acknowledge paralysis, to the extreme degree of asserting that a paralyzed arm is pointing to a nose, or that it doesn't belong to the patient at all.
Ramachandran claims that humor and laughter can also be explained by these hemispheric differences, based on the well-established notion that a joke leads you along one path, then suddenly surprises you with a trick ending. In this case both hemispheres are functioning normally: the left follows the story as it builds up, while the right fulfils its usual role of looking for anomalies. The punchline is exactly the sort of incongruity or unexpected twist that the right hemisphere seizes on, but in the case of a joke, it turns out to be trivial. So the tension that has built up (and always does when something truly novel and perhaps threatening happens in real life) must be dissipated, and we accomplish that by laughing. Ramachandran even goes on to suggest that the loud repetitive nature of laughter can be traced to our evolutionary past, when it was an alert to others that something strange--which every right hemisphere in the group had been tracking--had turned out to be trivial. I laugh and the rest of you can relax: that rustling wasn't a rattlesnake, it was a dung beetle.
(Our closest relatives, the chimpanzees, laugh as well, but do it much differently than we do, by inhaling and exhaling rapidly. Although this is not at all the way we laugh, it might still be explained by Ramachandran's theory.)
I am intrigued by these ideas, and it is easy to see how it explains the laughter of relief when something you fear turns out to be harmless. But does it explain why an infant laughs (or at least gurgles) when an adult says, "Goo goo ga ga"? Nor is it clear how Ramachandran would explain what the late Benjamin Spock described as the first joke ever told: the passing of wind. As any parent knows, that general subject provokes uproarious laughter at any time in any situation. Maybe there are some specialized brain circuits involved.
I can't leave the subject of laughing (and why we do it) without addressing tickling (and why we can't do it to ourselves). And wouldn't you know it--when something is biological you can almost guarantee that Charles Darwin had something to say about it, and that what he said still has a grain of truth in it. In 1872 Darwin drew an analogy between laughter and tickling: "The imagination is sometimes said to be tickled by a ludicrous idea; and this so-called tickling of the mind is curiously analogous with the body ... The touch must be light, and an idea or event, to be ludicrous, must not be of grave import."
Darwin observed that people who are ticklish are also people who laugh easily for other reasons. They tend to get goosebumps, to blush, and to cry. He suspected these physical phenomena were somehow related. In 1990 Alan Fridlund and Jennifer Loftis, psychologists at the University of California at Santa Barbara, tested these ideas and found them to be true: blushing, laughing, ticklishness, crying, and goosebumps go together. Fridlund and Loftis point out that laughing and crying are sometimes interchangeable ("I laughed until the tears rolled down my face") and that they might both be ways of releasing the tension that is obviously associated with blushing and goosebumps. And although they think there must be a strong genetic component to these related behaviors, they also point out that the environment plays a role. The parental habit of tickling infants to make them laugh establishes the connection between them (and sometimes crying) early in life. The authors did admit that much more study would have to be done.
But while tickling appears to be part of an emotional package, it is curious in and of itself: we want it to end as quickly as possible but we're laughing ourselves silly at the same time. It is probably that need to escape that explains why we can't tickle ourselves: when someone else is doing it we can't be sure they will stop. However, a shorthand explanation like that isn't good enough for psychologists who have actually tried to answer the question, "Why can't we tickle ourselves?" in the lab.
Nearly thirty years ago a team of British psychologists published a report in the journal Nature called "Preliminary Observations on Tickling Oneself." Rather than speculate, they built a tickling box, a complicated thing about the size of a shoebox with a slot in the top. A plastic pointer could be moved along the slot by a handle, and it would tickle the sole of a foot placed on the box. The pointer was cleverly counterweighted so as to exert the same pressure no matter how it was being moved.
Thirty undergraduate students were tickled in different ways: either the experimenter controlled the pointer, or the student did; or the student held the handle passively while the experimenter moved it. The results were more or less what you'd expect. Self-tickling didn't work; being tickled by the experimenter did, but holding the handle passively had an effect that was in between.
A few years later Guy Claxton at the University of London confirmed these findings by showing that subjects were more ticklish if they were being tickled by someone else (five light strokes with a feather in five seconds) than if they held the feather in their own hand but had the hand moved by another person. Apparently the sensation of movement reduces the ticklishness even if the subject isn't in control of the movement. He also found that subjects were more ticklish if they had their eyes closed--the surprise tickle--something that Darwin had suggested. As I was writing this chapter, a new experiment was reported that produced images of the brain during tickling. Those images revealed that, in the case of self-tickling, the cerebellum, a part of the brain responsible for coordinating movements, is activated. Furthermore, the cerebellum might then warn other parts of the brain that a tickle is on its way, dramatically reducing the sensation. When another person does the tickling, the brain's cerebellum is inactive and no warning is sent.
However, the children I know laugh harder when they know exactly where and when they are going to be tickled--the tickle of anticipation. Maybe in their case the cerebellum's warning heightens, rather than dampens, the tickle. Why children are different is not yet well understood.
That last phrase is a good description of the scientific understanding of laughter. There are suggestions, hints, some experiments that shed light on the complex relationship between humor, tickling, laughter, and the brain, but we are still far short of understanding why we respond to funny situations (and sometimes ones that aren't funny at all) with repetitive blasts of air. It almost brings on abrupt expirations due to a sudden contraction of the intercostal muscles.
Copyright © 1998 Jay Ingrain. All rights reserved.
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