the science of laughs

The Science of Laughs

Laughing out loud: scientists have made new discoveries about laughter.

Scanning brains and eavesdropping on chimps, researchers are figuring out why we

chuckle, guffaw and crack up. Hint: it isn’t funny.

By Sharon Begley, NEWSWEEK

NEWSWEEK October 9 issue — The man was known around town as a chronic

borrower, always asking the neighbors to lend him one tool or another. So when he

strolled over to Mr. Green one Sunday and asked, “Say, are you using your lawn mower

today?” Green had a ready answer. “Yes, I am,” he said emphatically.

TO WHICH THE would-be borrower replied, “Great! Then since you won’t need your

golf clubs, I’ll just borrow those.”

If you are like most people, that punch line triggered at least one short exhalation of

breath chopped into staccato segments lasting about one fifteenth of a second each and

spaced one fifth of a second apart. In other words, laughter. Exactly why humor causes

this acoustic response—rather than, say, sweaty palms or any other physiological

reaction—has been lost in the mists of evolution. Thinkers from Plato and Aristotle to

Kant, Darwin and Freud have tried to fathom laughter (Plato feared it would disrupt the

state, and Kant theorized that it arises when what you expect to happen doesn’t, which is

why surprising punch lines work), but they’ve been long on philosophy and short on

science.

Lately, though, an intrepid band of researchers has been trying to remedy that. With

techniques like MRI brain scans to probe why people cannot tickle themselves into

paroxysms of laughter, they are tackling “one of the last great unsolved problems in

human behavior,” says neuroscientist Robert Provine of the University of Maryland,

whose book, “Laughter: A Scientific Investigation,” will be published next week. And

no, he’s not referring to why guys are always walking into bars with ducks under their

arms.

To investigate the roots of laughter, scientists have turned to our primate cousins. If you

tickle a chimp (carefully; and preferably a baby), it will likely laugh, but the sound

doesn’t resemble human laughter so much as it does panting, with one sound per inhale

and exhale. Provine realized that the reason chimps cannot emit a string of “ho ho ho’s”

is that they cannot make more than a single sound when they exhale or inhale. Humans,

in contrast, can chop up a single exhalation into multiple bursts of “ha ha ha”—or words.

(Speech results from chopping up an exhalation into separate sounds.) “Laughter,” says

Provine, “is a probe into such fundamental questions as why humans can speak but other

apes can’t.” No humanlike laughing, no speaking.

The fact that chimps pant while playing suggests that laughter evolved from the heavy

breathing that accompanies something like playful wrestling. Ritualized panting—

laughter—then might have come to represent the playful activity itself, signaling, “I’m

enjoying this.” For there is no question that human laughter is a social behavior. (You

would have laughed more at the borrow-the-mower joke if you had heard it read aloud

while in a group, rather than reading it silently and alone.)

But what do titters communicate? Some clues come from Provine’s collection of 1,200

“laugh episodes,” from eavesdropping in public places. He finds that speakers laugh more

than listeners, and women laugh at men more than vice versa. (Laughing behind their

backs doesn’t count.)

Laughter seems to signal an attempt to ingratiate oneself: in India, notes Provine, men of

lower castes giggle when addressing men of higher castes, but never the other way round.

People in power seldom giggle. More evidence that laughing has less to do with humor

than with social signals is that, in Provine’s 1,200 samples, by far the remarks that most

often elicited laughter were of the “it was nice meeting you, too” or “I know” variety. In

other words, witless.

“Laughter is only rarely a response to jokes,” says Provine. “It is, instead, the

quintessential human social signal. It solidifies relationships and pulls people into the

fold.” And not only for the good. The Columbine killers laughed as they shot,

demonstrating solidarity with each other and, needless to say, not their targets. Evil

laughter is no oxymoron.

Laughter is contagious, for reasons that remain pretty murky, but while you can catch it

from others you can’t induce it in yourself. Forced laughter sounds, well, forced.

And tickling yourself is a non-starter. There have been all sorts of theories about why, but

recent experiments led by Sarah-Jayne Blakemore of University College, London, may

have finally revealed the answer. The neuroscientists used functional MRI to

(noninvasively) peer into the brains of volunteers who either tickled themselves or were

tickled by a robotic tickler. The MRI detected more neuronal activity in the

somatosensory cortex, the part of the brain that registers touch, when people were tickled

than when they tickled themselves. The reason seems to be that when you move your

fingers to, say, tickle your rib cage, the cerebellum, which coordinates complex

movements, predicts what that will feel like—and sends out a signal to cancel the sensory

response much as the military can jam an enemy radio transmission if it knows the

frequency ahead of time. But if the tickle comes from someone else, and so is a surprise,

the cerebellum can’t block it. Self-tickling thus seems to make neurons fire in a way that

blocks activation of the part of the brain that ordinarily processes touch.

Laughter seems intimately entwined with our physiology. It blocks a neural reflex that

regulates muscle tone, proving that “going weak with laughter” is more than a metaphor.

Tumors or lesions of the brain’s hypothalamus, which regulates basic processes like

respiration, can cause bouts of uncontrolled laughter. And although laughter seems to

have evolved because of the message it sends to others, it may have a therapeutic effect

on the laugher, too: it can raise heart rate as much as aerobic exercise, lessen the

perception of pain and increase tolerance of discomfort. While the scientists work out

how a good chuckle does all this, have you heard the one about the priest, the minister

and the rabbi... ?

source : Randall Munson