Humans wired to cooperate

Diane Monaco dmonaco at pop3.utoledo.edu
Tue Jul 23 06:14:50 PDT 2002


NY Times

July 23, 2002

Why We're So Nice: We're Wired to Cooperate

By NATALIE ANGIER

What feels as good as chocolate on the tongue or money in the bank but

won't make you fat or risk a subpoena from the Securities and Exchange

Commission?

Hard as it may be to believe in these days of infectious greed and

sabers unsheathed, scientists have discovered that the small, brave

act of cooperating with another person, of choosing trust over

cynicism, generosity over selfishness, makes the brain light up with

quiet joy.

Studying neural activity in young women who were playing a classic

laboratory game called the Prisoner's Dilemma, in which participants

can select from a number of greedy or cooperative strategies as they

pursue financial gain, researchers found that when the women chose

mutualism over "me-ism," the mental circuitry normally associated with

reward-seeking behavior swelled to life.

And the longer the women engaged in a cooperative strategy, the more

strongly flowed the blood to the pathways of pleasure.

The researchers, performing their work at Emory University in Atlanta,

used magnetic resonance imaging to take what might be called portraits

of the brain on hugs.

"The results were really surprising to us," said Dr. Gregory S. Berns,

a psychiatrist and an author on the new report, which appears in the

current issue of the journal Neuron. "We went in expecting the

opposite."

The researchers had thought that the biggest response would occur in

cases where one person cooperated and the other defected, when the

cooperator might feel that she was being treated unjustly.

Instead, the brightest signals arose in cooperative alliances and in

those neighborhoods of the brain already known to respond to desserts,

pictures of pretty faces, money, cocaine and any number of licit or

illicit delights.

"It's reassuring," Dr. Berns said. "In some ways, it says that we're

wired to cooperate with each other."

The study is among the first to use M.R.I. technology to examine

social interactions in real time, as opposed to taking brain images

while subjects stared at static pictures or thought-prescribed

thoughts.

It is also a novel approach to exploring an ancient conundrum, why are

humans so, well, nice? Why are they willing to cooperate with people

whom they barely know and to do good deeds and to play fair a

surprisingly high percentage of the time?

Scientists have no trouble explaining the evolution of competitive

behavior. But the depth and breadth of human altruism, the willingness

to forgo immediate personal gain for the long-term common good, far

exceeds behaviors seen even in other large-brained highly social

species like chimpanzees and dolphins, and it has as such been

difficult to understand.

"I've pointed out to my students how impressive it is that you can

take a group of young men and women of prime reproductive age, have

them come into a classroom, sit down and be perfectly comfortable and

civil to each other," said Dr. Peter J. Richerson, a professor of

environmental science and policy at the University of California at

Davis and an influential theorist in the field of cultural evolution.

"If you put 50 male and 50 female chimpanzees that don't know each

other into a lecture hall, it would be a social explosion."

Dr. Ernst Fehr of the University of Zurich and colleagues recently

presented findings on the importance of punishment in maintaining

cooperative behavior among humans and the willingness of people to

punish those who commit crimes or violate norms, even when the

chastisers take risks and gain nothing themselves while serving as ad

hoc police.

In her survey of the management of so-called commons in small-scale

communities where villagers have the right, for example, to graze

livestock on commonly held land, Dr. Elinor Ostrom of Indiana

University found that all communities have some form of monitoring to

gird against cheating or using more than a fair share of the resource.

In laboratory games that mimic small-scale commons, Dr. Richerson

said, 20 to 30 percent have to be coerced by a threat of punishment to

cooperate.

Fear alone is not highly likely to inspire cooperative behavior to the

degree observed among humans. If research like Dr. Fehr's shows the

stick side of the equation, the newest findings present the neural

carrot - people cooperate because it feels good to do it.

In the new findings, the researchers studied 36 women from 20 to 60

years old, many of them students at Emory and inspired to participate

by the promise of monetary rewards. The scientists chose an all-female

sample because so few brain-imaging studies have looked at only women.

Most have been limited to men or to a mixture of men and women.

But there is a vast body of non- imaging data that rely on using the

Prisoner's Dilemma.

"It's a simple and elegant model for reciprocity," said Dr. James K.

Rilling, an author on the Neuron paper who is at Princeton. "It's been

referred to as the E. coli of social psychology."

From past results, the researchers said, one can assume that neuro-

imaging studies of men playing the game would be similar to their new

findings with women.

The basic structure of the trial had two women meet each other briefly

ahead of time. One was placed in the scanner while the other remained

outside the scanning room. The two interacted by computer, playing

about 20 rounds of the game. In every round, each player pressed a

button to indicate whether she would "cooperate" or "defect." Her

answer would be shown on-screen to the other player.

The monetary awards were apportioned after each round. If one player

defected and the other cooperated, the defector earned $3 and the

cooperator nothing. If both chose to cooperate, each earned $2. If

both opted to defect, each earned $1.

Hence, mutual cooperation from start to finish was a far more

profitable strategy, at $40 a woman, than complete mutual defection,

which gave each $20.

The risk that a woman took each time she became greedy for a little

bit more was that the cooperative strategy would fall apart and that

both would emerge the poorer.

In some cases, both women were allowed to pursue any strategy that

they chose. In other cases, the non- scanned woman would be a

"confederate" with the researchers, instructed, unbeknown to the

scanned subject, to defect after three consecutive rounds of

cooperation, the better to keep things less rarefied and pretty and

more lifelike and gritty.

In still other experiments, the woman in the scanner played a computer

and knew that her partner was a machine. In other tests, women played

a computer but thought that it was a human.

The researchers found that as a rule the freely strategizing women

cooperated. Even occasional episodes of defection, whether from free

strategizers or confederates, were not necessarily fatal to an

alliance.

"The social bond could be reattained easily if the defector chose to

cooperate in the next couple of rounds," another author of the report,

Dr. Clinton D. Kilts, said, "although the one who had originally been

`betrayed' might be wary from then on."

As a result of the episodic defections, the average per-experiment

take for the participants was in the $30's. "Some pairs, though, got

locked into mutual defection," Dr. Rilling said.

Analyzing the scans, the researchers found that in rounds of

cooperation, two broad areas of the brain were activated, both rich in

neurons able to respond to dopamine, the brain chemical famed for its

role in addictive behaviors.

One is the anteroventral striatum in the middle of the brain right

above the spinal cord. Experiments with rats have shown that when

electrodes are placed in the striatum, the animals will repeatedly

press a bar to stimulate the electrodes, apparently receiving such

pleasurable feedback that they will starve to death rather than stop

pressing the bar.

Another region activated during cooperation was the orbitofrontal

cortex in the region right above the eyes. In addition to being part

of the reward-processing system, Dr. Rilling said, it is also involved

in impulse control.

"Every round, you're confronted with the possibility of getting an

extra dollar by defecting," he said. "The choice to cooperate requires

impulse control."

Significantly, the reward circuitry of the women was considerably less

responsive when they knew that they were playing against a computer.

The thought of a human bond, but not mere monetary gain, was the

source of contentment on display.

In concert with the imaging results, the women, when asked afterward

for summaries of how they felt during the games, often described

feeling good when they cooperated and expressed positive feelings of

camaraderie toward their playing partners.

Assuming that the urge to cooperate is to some extent innate among

humans and reinforced by the brain's feel-good circuitry, the question

of why it arose remains unclear. Anthropologists have speculated that

it took teamwork for humanity's ancestors to hunt large game or gather

difficult plant foods or rear difficult children. So the capacity to

cooperate conferred a survival advantage on our forebears.

Yet as with any other trait, the willingness to abide by the golden

rule and to be a good citizen and not cheat and steal from one's

neighbors is not uniformly distributed.

"If we put some C.E.O.'s in here, I'd like to see how they respond,"

Dr. Kilts said. "Maybe they wouldn't find a positive social

interaction rewarding at all."

A Prisoner's Dilemma indeed.



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