Phantoms in the Brain: Probing the Mysteries of the Human Mind (35 page)

mically 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 139

tissue at the focal point of her seizures and were exploring nearby areas to make sure they did not re −move 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 unexpectedre−sponse. 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).

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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 café 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 141

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.