By Alison McCook
NEW YORK (Reuters Health) - People appear
to have an innate ability to determine when someone is cheating them
out of a deal, US researchers suggest.
In one recent report, a group of
investigators demonstrate that humans from widely different
cultures--US college students and members of an Amazonian
society--can identify when someone is reneging on some type of
social agreement, suggesting this ability may be an aspect of being
In another related article, the authors
report the experience of a man who suffered damage to one portion of
the brain in a bicycle accident and lost the ability to detect a
cheater. However, he remained able to reason and express emotions,
demonstrating that the ability may be linked to a particular region
of the brain.
The research centers on the principle of
social contracts, in which one person offers to do something for the
other, who then offers something in return. The process, known as a
social exchange, includes situations such as when people hold
potlucks, or when a buyer pays $5 for a sandwich.
Researchers have spotted this behavior in
a variety of species besides humans, ranging from bats to baboons.
Although it is often in the interest of animals to help blood
relatives without the promise of a return reward, in other cases,
indiscriminately performing favors for others can hurt chances of
survival, said study author Dr. John Tooby of the University of
California, Santa Barbara.
According to Tooby, individuals who enter
into social exchanges without determining whether the participant
will cheat them out of the return favor will become exploited over
time, and are less likely to reproduce and pass on their
Consequently, those who try not to let
themselves become exploited during social exchanges are more likely
to live long enough to reproduce and distribute their genes to the
next generation. But in order to do that, "you have to notice when
you're being exploited," Tooby said.
In two articles published in the early
edition of the Proceedings of the National Academy of Sciences,
Tooby and his colleagues offer evidence to support the theory that
humans are born with the capacity to identify people who cheat
during social exchanges.
In one study, Tooby and his team
demonstrate that members of the Shiwiar, who live in a remote region
of the Ecuadorian Amazon and do not read or regularly contact
outsiders, are just as able to detect when people might cheat in
social exchanges as Harvard undergraduates.
In the other article, the investigators
describe the experience of a patient dubbed R.M., who suffered
damage to a particular area of the brain during a bike accident.
Thereafter, the man performed poorly during tests of the nature of
social exchanges, but lacked neither emotions nor the ability to
complete tests that targeted other types of reasoning.
In an interview with Reuters Health,
Tooby explained that, taken together, these results demonstrate that
the ability to notice when you are being cheated on social exchanges
may be linked to a particular area of the brain, and that people can
develop that ability regardless of their own cultural
"If (detecting cheaters in social
exchanges) were all culturally specific, then you should find some
cultures where people don't do it. We don't think that's the case,"
He cautioned that the results from R.M.
do not necessarily indicate that proficiency in assessing social
exchanges resides wholly in the patient's damaged brain region. The
man had damage to the limbic system, which is associated with
"But the fact that damage to that area
knocks something out indicates that region plays a role," he
SOURCE: Proceedings of the National
Academy of Sciences Early Edition