Книга: Phantoms in the Brain

CHAPTER 10 The Woman Who Died Laughing

CHAPTER 10

The Woman Who Died Laughing

On the morning of his mother’s funeral in 1931, Willy Anderson — a twenty-five-year-old plumber from London — donned a new black suit, clean white shirt and nice shoes borrowed from his brother. He had loved his mother very much and his grief was palpable. The family gathered amid tearful hugs and sat silently through an hour-long funeral service in a church that was much too hot and stuffy. Willy was relieved finally to get outdoors into the chilly open air of the cemetery and bow his head with the rest of the family and friends. But just as the gravediggers began lowering his mother’s roped casket into the earth, Willy began to laugh. It started as a muffled snorting sound that evolved into a prolonged giggle. Willy bowed his head farther down, dug his chin into his shirt collar and drew his right hand up to his mouth, trying to stifle the unbidden mirth. It was no use. Against his will and to his profound embarrassment, he began to laugh out loud, the sounds exploding rhythmically until he doubled over. Everyone at the funeral stared, mouth agape, as the young man staggered backward, desperately looking for retreat. He walked bent at the waist, as if in supplication for forgiveness for the laughter that would not subside. The mourners could hear him at the far end of the cemetery, his laughter echoing amid the gravestones.

That evening, Willy’s cousin took him to the hospital. The laughter had subsided after some hours, but it was so inexplicable, so stunning in its inappropriateness, that everyone in the family felt it should be treated as a medical emergency. Dr. Astley Clark, the physician on duty, examined Willy’s pupils and checked his vital signs. Two days later, a nurse found Willy lying unconscious in his bed, having suffered a severe subarachnoid hemorrhage, and he died without regaining consciousness. The postmortem showed a large ruptured aneurysm in an artery at the base of his brain that had compressed part of his hypothalamus, mammillary bodies and other structures on the floor of his brain.

And then there was Ruth Greenough, a fifty-eight-year-old librarian from Philadelphia. Although she had suffered a mild stroke, she was able to keep her small branch library running smoothly. But one morning in 1936, Ruth had a sudden violent headache, and within seconds her eyes turned up and she was seized with a laughing fit. She began shaking with laughter and couldn’t stop. Short expirations followed each other in such rapid succession that Ruth’s brain grew oxygen-starved and she broke into a sweat, at times holding her hand to her throat as if she were choking. Nothing she did would stop the convulsions of laughter, and even an injection of morphine given by the doctor had no effect. The laughter went on for an hour and a half. All the while, Ruth’s eyes remained turned upward and wide open. She was conscious and could follow her doctor’s instructions but was not able to utter a single word. At the end of an hour and a half, Ruth lay down completely exhausted. The laughter persisted but was noiseless — little more than a grimace. Suddenly she collapsed and became comatose, and after twenty-four hours Ruth died. I can say that she literally died laughing. The postmortem revealed that a cavity in the middle of her brain (called the third ventricle) was filled with blood. A hemorrhage had occurred, involving the floor of her thalamus and compressing several adjacent structures. The English neurologist Dr. Purdon Martin, who described Ruth’s case, said, “The laughter is a mock or sham and it mocks the laughter at the time, but this is the greatest mockery of all, that the patient should be forced to laugh as a portent of his own doom.”¹

More recently, the British journal Nature reported a modern case of laughter elicited by direct electrical stimulation of the brain during surgery. The patient was a fifteen-year-old girl named Susan who was being treated for intractable epilepsy. Doctors hoped to excise the tissue at the focal point of her seizures and were exploring nearby areas to make sure they did not remove any critically important functions. When the surgeon stimulated Susan’s supplementary motor cortex (close to a region in the frontal lobes that receives input from the brain’s emotional centers), he got an unexpected response. Susan started laughing uncontrollably, right on the operating table (she was awake for the procedure). Oddly enough, she ascribed her merriment to everything she saw around her, including a picture of a horse, and added that the people standing near her looked incredibly funny. To the doctors, she said: “You guys are just so funny standing around”.²

The kind of pathological laughter seen in Willy and Ruth is rare; only a couple of dozen such cases have been described in the medical literature. But when you gather them together, a striking fact jumps out at you. The abnormal activity or damage that sets people giggling is almost always located in portions of the limbic system, a set of structures including the hypothalamus, mammillary bodies and cingulate gyrus that are involved in emotions (see Figure 8.1). Given the complexity of laughter and its infinite cultural overtones, I find it intriguing that a relatively small cluster of brain structures is behind the phenomenon — a sort of “laughter circuit”.

But identifying the location of such a circuit doesn’t tell us why laughter exists or what its biological function might be. (You can’t say it evolved because it feels good. That would be a circular argument, like saying sex exists because it feels good instead of saying it feels good because it motivates you to spread your genes.) Asking why a given trait evolved (be it yawning, laughing, crying or dancing) is absolutely vital for understanding its biological function, and yet this question is rarely raised by neurologists who study patients with brain lesions. This is astonishing given that the brain was shaped by natural selection just as any other organ in the body, such as the kidney, liver or pancreas, was.

Fortunately, the picture is changing, thanks in part to “evolutionary psychology”, the new discipline that I mentioned in the last chapter.³ The central tenet of this controversial field is that many salient aspects of human behavior are mediated by specialized modules (mental organs) that were specifically shaped by natural selection. As our Pleistocene ancestors romped across ancient savannas in small probands, their brains evolved solutions to their everyday problems — things like recognizing kin, seeking healthy sexual partners or eschewing foul-smelling food.

For example, evolutionary psychologists would argue that your disgust for feces — far from being taught to you by your parents — is probably hard-wired in your brain. Since feces might contain infectious bacteria, eggs and parasites, those ancestral hominids who had “disgust for feces” genes survived and passed on those genes, whereas those who didn’t were wiped out (unlike dung beetles, who probably find the bouquet of feces irresistible). This idea may even explain why feces infected with cholera, salmonellosis or shigella are especially foul smelling.⁴

Evolutionary psychology is one of those disciplines that tend to polarize scientists. You are either for it or vehemently against it with much arm waving and trading of raspberries behind backs, much as people are nativists (genes specify everything) or empiricists (the brain is a blank slate whose wiring is subsequently specified by the environment, including culture). The real brain, it turns out, is far messier than what’s implied by these simple-minded dichotomies. For some traits — and I’m going to argue that laughter is one of them — the evolutionary perspective is essential and helps explain why a specialized laughter circuit exists. For other traits this way of thinking is a waste of time (as we noted in Chapter 9, the notion that there might be genes or mental organs for cooking is silly, even though cooking is a universal human trait).

The distinction between fact and fiction gets more easily blurred in evolutionary psychology than in any other discipline, a problem that is exacerbated by the fact that most “ev-psych” explanations are completely untestable: You can’t run experiments to prove or disprove them. Some of the proposed theories — that we have genetically specified mechanisms to help us detect fertile mates or that women suffer from morning sickness to protect the fetus from poisons in foods — are ingenious. Others are ridiculously far-fetched. One afternoon, in a whimsical mood, I sat down and wrote a spoof of evolutionary psychology just to annoy my colleagues in that field. I wanted to see how far one could go in conjuring up completely arbitrary, ad hoc, untestable evolutionary explanations for aspects of human behavior that most people would regard as “cultural” in origin. The result was a satire titled “Why Do Gentlemen Prefer Blondes?” To my amazement, when I submitted my tongue-in-cheek essay to a medical journal, it was promptly accepted. And to my even greater surprise, many of my colleagues did not find it amusing; to them it was a perfectly plausible argument, not a spoof.⁵ (I describe it in the endnotes in case you are curious.)

What about laughter? Can we come up with a reasonable evolutionary explanation, or will the true meaning of laughter remain forever elusive?

If an alien ethologist were to land on earth and watch us humans, he would be mystified by many aspects of our behavior, but I’ll wager that laughter would be very near the top of the list. As he watches people interacting, he notices that every now and then we suddenly stop what we’re doing, grimace and make a loud repetitive sound in response to a wide variety of situations. What function could this mysterious behavior possibly serve? Cultural factors undoubtedly influence humor and what people find funny — the English are thought to have a sophisticated sense of humor, whereas Germans or Swiss, it is said, rarely find anything amusing. But even if this is true, might there still be some sort of “deep structure” underlying all humor? The details of the phenomenon vary from culture to culture and are influenced by the way people are raised, but this doesn’t mean there’s no genetically specified mechanism for laughter — a common denominator underlying all types of humor. Indeed, many people have suggested that such a mechanism does exist, and theories on the biological origins of humor and laughter have a long history, going all the way to Schopenhauer and Kant, two singularly humorless German philosophers.

Consider the following two jokes. (Not surpisingly, it was difficult to find examples that are not racist, sexist or ethnic. After a diligent search I found one that was and one that wasn’t.)

A fellow is sitting in a truck stop caf? in California, having lunch, when suddenly a giant panda bear walks in and orders a burger with fries and a chocolate milkshake. The bear sits down, eats the food, then stands up, shoots several of the other customers and runs out the door. The fellow is astonished, but the waiter seems completely undisturbed. “What the hell is going on?” the customer asks. “Oh, well, there’s nothing surprising about that”, says the waiter. “Just go look in the dictionary under ‘panda’.” So the guy goes to the library, takes out a dictionary and looks up “panda” — a big furry, black and white animal that lives in the rain forest of China. It eats shoots and leaves.

A guy carrying a brown paper bag goes into a bar and orders a drink. The bartender smiles, pours the drink and then, unable to contain his curiosity, says, “So, what’s in the bag?” The man gives a little laugh and says, “You wanna see? Sure, you can see what’s in the bag”, and he reaches in and pulls out a tiny piano, no more than six inches tall. “What’s that?” asks the bartender. The man doesn’t say anything; he just reaches into the bag a second time and pulls out a tiny man, about a foot tall, and sits him down next to the piano. “Wow”, says the bartender, absolutely astonished. “I’ve never in my life seen anything like that.” The little man begins to play Chopin. “Holy cow”, says the bartender, “where did you ever get him?” The man sighs and says, “Well, you see, I found this magic lamp and it has a genie in it. He can grant you anything you want but only gives one wish.” The bartender scowls, “Oh, yeah, sure you do. Who are you trying to kid?” “You don’t believe me?” says the man, somewhat offended. He reaches into his coat pocket and pulls out a silver lamp with an ornate curved handle. “Here it is. Here’s the lamp with the genie in it. Go ahead and rub it if you don’t believe me.” So the bartender pulls the lamp over to his side of the counter and, looking at the man skeptically, rubs the lamp. And then POOF, a genie appears over the bar, bows to the bartender and says, “Sire, your wish is my command. I shall grant thee one wish and one wish only.” The bartender gasps but quickly gains his composure and says, “Okay, okay, give me a million bucks!” The genie waves his wand and all of a sudden the room is filled with tens of thousands of quacking ducks. They’re all over the place, making a terrible noise: Quack, quack, quack! The bartender turns to the man and says, “Hey! What’s the matter with this genie? I asked for a million bucks and I get a million ducks. Is he deaf or something?” The man looks at him and replies, “Well, do you really think I asked for a twelve-inch pianist?”

Why are these stories funny? And what do they have in common with other jokes? Despite all their surface diversity, most jokes and funny incidents have the following logical structure: Typically you lead the listener along a garden path of expectation, slowly building up tension. At the very end, you introduce an unexpected twist that entails a complete reinterpretation of all the preceding data, and moreover, it’s critical that the new interpretation, though wholly unexpected, makes as much “sense” of the entire set of facts as did the originally “expected” interpretation. In this regard, jokes have much in common with scientific creativity, with what Thomas Kuhn calls a “paradigm shift” in response to a single “anomaly”. (It’s probably not coincidence that many of the most creative scientists have a great sense of humor.) Of course, the anomaly in the joke is the traditional punch line and the joke is “funny” only if the listener gets the punch line by seeing in a flash of insight how a completely new interpretation of the same set of facts can incorporate the anomalous ending.

The longer and more tortuous the garden path of expectation, the “funnier” the punch line when finally delivered. Good comedians make use of this principle by taking their time to build up the tension of the story line, for nothing kills humor more surely than a premature punch line.

But although the introduction of a sudden twist at the end is necessary for the genesis of humor, it is certainly not sufficient. Suppose my plane is about to land in San Diego and I fasten my seat belt and get ready for touchdown. The pilot suddenly announces that the “bumps” that he (and I) had earlier dismissed as air turbulence are really due to engine failure and that we need to empty fuel before landing. A paradigm shift has occurred in my mind, but this certainly does not make me laugh. Rather, it makes me orient toward the anomaly and prepare for action to cope with the anomaly. Or consider the time I was staying at some friends’ house in Iowa City. They were away and I was alone in unfamiliar surroundings. It was late at night and just as I was about to doze off, I heard a thump downstairs. “Probably the wind”, I thought. After a few minutes there was another thud, louder than the one before. Again I “rationalized” it away and went back to sleep.

Twenty minutes later I heard an extremely loud, resounding “bang” and leapt out of bed. What was happening? A burglar perhaps? Naturally, with my limbic system activated, I “oriented”, grabbed a flashlight and ran down the stairs. Nothing funny so far. Then, suddenly I noticed a large flower vase in pieces on the floor and a large tabby cat right next to it — the obvious culprit! In contrast to the airplane incident, this time I started laughing because I realized that the “anomaly” I had detected and the subsequent paradigm shift were of trivial consequence. All of the facts could now be explained in terms of the cat theory rather than the ominous burglar theory.

On the basis of this example, we can sharpen our definition of humor and laughter. When a person strolls along a garden path of expectation and there is a sudden twist at the end that entails a complete reinterpretation of the same facts and the new interpretation has trivial rather than terrifying implications, laughter ensues.

But why laughter? Why this explosive, repetitive sound? Freud’s view that laughter discharges pent-up internal tension does not make much sense without recourse to an elaborate and far-fetched hydraulic metaphor. He argued that water building up in a system of pipes will find its way out of the path of least resistance (the way a safety valve opens when too much pressure builds up in a system), and laughter might provide a similar safety valve to allow the escape of psychic energy (whatever that might mean). This “explanation” really doesn’t work for me; it belongs to a class of explanations that Peter Medawar has called “analgesics” that “dull the ache of incomprehension without removing the cause”.

To an ethologist, on the other hand, any stereotyped vocalization almost always implies that the organism is trying to communicate something to others in the social group. Now what might this be in the case of laughter? I suggest that the main purpose of laughter might be to allow the individual to alert others in the social group (usually kin) that the detected anomaly is trivial, nothing to worry about. The laughing person in effect announces her discovery that there has been a false alarm; that the rest of you chaps need not waste your precious energy and resources responding to a spurious threat.⁶ This also explains why laughter is so notoriously contagious, for the value of any such signal would be amplified as it spread through the social group.

This “false alarm theory” of humor may also explain slapstick. You watch a man — preferably one who is portly and self-important — walk down the street when suddenly he slips on a banana peel and falls down. If his head hit the pavement and his skull split open, you would not laugh as you saw blood spill out; you would rush to his aid or to the nearest telephone to call an ambulance. But if he got up casually, wiped the remains of the fruit from his face and continued walking, you would probably burst out laughing, thereby letting others standing nearby know that they need not rush to his aid. Of course, when watching Laurel and Hardy or Mr. Bean, we are more willing to tolerate “real” harm or injury to the hapless victim because we are fully aware that it’s only a movie.

Although this model accounts for the evolutionary origin of laughter, it by no means explains all the functions of humor among modern humans. Once the mechanism was in place, however, it could easily be exploited for other purposes. (This is common in evolution. Feathers evolved in birds originally to provide insulation but were later adapted for flying.) The ability to reinterpret events in the light of new information may have been refined through the generations to help people playfully juxtapose larger ideas or concepts — that is, to be creative. This capacity for seeing familiar ideas from novel vantage points (an essential element of humor) could be an antidote to conservative thinking and a catalyst to creativity. Laughter and humor may be a dress rehearsal for creativity, and if so, perhaps jokes, puns and other forms of humor should be introduced very early into our elementary schools as part of the formal curriculum.⁷

Although these suggestions may help explain the logical structure of humor, they do not explain why humor itself is sometimes used as a psychological defense mechanism. Is it a coincidence, for example, that a disproportionate number of jokes deal with potentially disturbing topics, such as death or sex? One possibility is that jokes are an attempt to trivialize genuinely disturbing anomalies by pretending they are of no consequence; you distract yourself from your anxiety by setting off your own false alarm mechanism. Thus a trait that evolved to appease others in a social group now becomes internalized to deal with truly stressful situations and may emerge as so-called nervous laughter. Thus even as mysterious a phenomenon as “nervous laughter” begins to make sense in the light of some of the evolutionary ideas discussed here.

The smile, too, may have similar evolutionary origins, as a “weaker” form of laughter. When one of your ancestral primates encountered another individual coming toward him from a distance, he may have initially bared his canines in a threatening grimace on the fair assumption that most strangers are potential enemies.

Upon recognizing the individual as “friend” or “kin”, however, he might abort the grimace halfway, thereby producing a smile, which in turn may have evolved into a ritualized human greeting: “I know you pose no threat and I reciprocate”.⁸ Thus in my scheme, a smile is an aborted orienting response in the same way that laughter is.

The ideas we have explored so far help explain the biological functions and possible evolutionary origin of humor, laughter and smiling, but they still leave open the question of what the underlying neural mechanisms of laughter might be. What about Willy, who started giggling at his mother’s funeral, and Ruth, who literally died laughing? Their strange behavior implies the existence of a laughter circuit found mainly in portions of the limbic system and its targets in the frontal lobes. Given the well-known role of the limbic system in producing an orienting response to a potenial threat or alarm, it is not altogether surprising, perhaps, that it is also involved in the aborted orienting reaction in response to a false alarm — laughter. Some parts of this circuit handle emotions — the feeling of merriment that accompanies laughter — whereas other parts are involved in the physical act itself, but at present we do not know which parts are doing what.

There is, however, another curious neurological disorder, called pain asymbolia, which offers additional hints about the neurological structures underlying laughter. Patients with this condition do not register pain when they are deliberately jabbed in the finger with a sharp needle. Instead of saying, “Ouch!” they say, “Doctor, I can feel the pain but it doesn’t hurt.” Apparently they do not experience the aversive emotional impact of pain. And, mysteriously, I have noticed that many of them actually start giggling, as if they were being tickled and not stabbed. For instance, in a hospital in Madras, India, I recently examined a schoolteacher who told me that a pinprick I administered as part of a routine neurology workup felt incredibly funny — although she couldn’t explain why.

I became interested in pain asymbolia mainly because it provides additional support for the evolutionary theory of laughter that I’ve proposed in this chapter. The syndrome is often seen when there is damage to a structure called the insular cortex — buried in the fold between the parietal and temporal lobes (and closely linked to the structures that were damaged in Willy and Ruth). This structure receives sensory input, including pain from the skin and internal organs, and sends its output to parts of the limbic system (such as the cingulate gyrus) so that one begins to experience the strong aversive reaction — the agony — of pain. Now imagine what would happen if the damage were to disconnect the insular cortex from the cingulate gyrus. One part of the person’s brain (the insular cortex) tells him, “Here is something painful, a potential threat”, while another part (the cingulate gyrus of the limbic system) says a fraction of a second later, “Oh, don’t worry; this is no threat after all.” Thus the two key ingredients — threat followed by deflation — are present, and the only way for the patient to resolve the paradox is to laugh, just as my theory would predict.

The same line of reasoning may help explain why people laugh when tickled.⁹ You approach a child, hand stretched out menacingly. The child wonders, “Will he hurt me or shake me or poke me?” But no, your fingers make light, intermittent contact with her belly. Again, the recipe — threat followed by deflation — is present and the child laughs, as if to inform other children, “He doesn’t mean harm. He’s only playing!” This, by the way, may help children practice the kind of mental play required for adult humor. In other words, what we call “sophisticated cognitive” humor has the same logical form as tickling and therefore piggybacks on the same neural circuits — the “threatening but harmless” detector that involves the insular cortex, cingulate gyrus and other parts of the limbic system. Such co-opting of mechanisms is the rule rather than the exception in the evolution of mental and physical traits (although in this case, the co-opting occurs for a related, higher-level function rather than for a completely different function).

These ideas have some bearing on a heated debate that has been going on among evolutionary biologists in general and evolutionary psychologists in particular during the last ten years. I get the impression that there are two warring camps. One camp implies (with disclaimers) that every one of our mental traits — or at least 99 percent of them — is specifically selected for by natural selection. The other camp, represented by Stephen Jay Gould, calls members of the first camp “ultra-Darwinists” and argues that other factors must be kept in mind. (Some of the factors pertain to the actual selection process itself and others to the raw material that natural selection can act on. They complement rather than contradict the idea of natural selection.) Every biologist I know has strong views on what these factors might be. Here are some of my favorite examples:

• What you now observe may be a bonus or useful by-product of something else that was selected for a completely different purpose. For example, a nose evolved for smelling and warming and moistening air but can also be used for wearing spectacles. Hands evolved for grasping branches but can now be used for counting as well.

• A trait may represent a further refinement (through natural selection) of another trait that was originally selected for a completely different purpose. Feathers evolved from reptilian scales to keep birds warm but have since been co-opted and transformed into wing feathers for flying; this is called preadaptation.

• Natural selection can only select from what is available, and what is available is often a very limited repertoire, constrained by the organism’s previous evolutionary history as well as certain developmental pathways that either are permanently closed or remain open.

I’d be very surprised if these three statements were not true to some extent regarding the many mental traits that constitute human nature. Indeed, there are many other principles of this sort (including plain old Lady Luck or contingency) that are not covered by the phrase “natural selection”.¹⁰ Yet ultra-Darwinists steadfastly adhere to the view that almost all traits, other than those obviously learned, are specific products of natural selection. For them, preadaptation, contingency and the like play only a minor role in evolution; they are “exceptions that prove the rule”. Moreover, they believe that you can in principle reverse engineer various human mental traits by looking at environmental and social constraints. (“Reverse engineering” is the idea that you can best understand how something works by asking what environmental challenge it evolved for. And then, working backward, you consider plausible solutions to that challenge. It is an idea that is popular, not surprisingly, with engineers and computer programmers.) As a biologist, I am inclined to go with Gould; I believe that natural selection is certainly the single most important driving force of evolution, but I also believe that each case needs to be examined individually. In other words, it is an empirical question whether some mental or physical trait that you observe in an animal or person was selected for by natural selection. Furthermore, there are dozens of ways to solve an environmental problem, and unless you know the evolutionary history, taxonomy and paleontology of the animal you are looking at, you cannot figure out the exact route taken by a particular trait (like feathers, laughter or hearing) as it evolved into its present form.

This is technically referred to as the “trajectory” taken by the trait “through the fitness landscape”.

My favorite example of this phenomenon involves the three little bones in our middle ear — the malleus, incus and stapes. Now used for hearing, two of these bones (the malleus and incus) were originally part of the lower jaw of our reptilian ancestors, who used them for chewing. Reptiles needed flexible, multielement, multihinged jaws so they could swallow giant prey, whereas mammals preferred a single strong bone (the dentary) for cracking nuts and chewing tough substances like grains. So as reptiles evolved into mammals, two of the jawbones were co-opted into the middle ear and used for amplifying sounds (partly because early mammals were nocturnal and relied largely on hearing for survival). This is such an ad hoc, bizarre solution that unless you know your comparative anatomy well or discovered fossil intermediates, you never could have deduced it from simply considering the functional needs of the organism. Contrary to the ultra-Darwinist view, reverse engineering doesn’t always work in biology for the simple reason that God is not an engineer; he’s a hacker.

What has all this got to do with human traits like smiling? Everything. If my argument concerning the smile is correct, then even though it evolved through natural selection, not every feature of a smile is adaptive for its current demand. That is, the smile takes the particular form that it does not because of natural selection alone but because it evolved from the very opposite — the threat grimace! There is no way you could deduce this through reverse engineering (or figure out its particular trajectory through the fitness landscape) unless you also know about the existence of canine teeth, knew that nonhuman primates bare their canines as a mock threat or knew that mock threats in turn evolved from real threat displays. (Big canines are genuinely dangerous.)

I find great irony in the fact that every time someone smiles at you she is in fact producing a half threat by flashing her canines. When Darwin published On the Origin of Species he delicately hinted in his last chapter that we too may have evolved from apelike ancestors. The English statesman Benjamin Disraeli was outraged by this and at a meeting held in Oxford he asked a famous rhetorical question: “Is man a beast or an angel?”

To answer this, he need only have looked at his wife’s canines as she smiled at him, and he’d have realized that in this simple universal human gesture of friendliness lies concealed a grim reminder of our savage past.

As Darwin himself concluded in The Descent of Man: