Brains sniff out scam
artistsEvolution might have
programmed us to compute fairness.
13 August 2002
|Wear the helmet, clean the
bike: different rules use different brain
The human brain contains dedicated circuits to detect
cheaters, say researchers1.
The same team has found that people from different
cultures are equally good at spotting unfair
Humans evolved cheat detection as a separate mental
component, says evolutionary psychologist John Tooby of
the University of California, Santa Barbara. "Our brains
have specialized programs like computer programs,
specific for various applications," he says.
Tooby and his colleagues tested the ability of a
patient called R.M. to detect cheats. R.M. has damage to
brain areas involved in emotion and social behaviour.
His intelligence is normal, but he has trouble working
out what other people know, think or feel.
The researchers gave R.M. either a social rule ("If
you borrow my motorcycle, you have to wash it") or a
precautionary rule ("If you ride a motorcycle, you must
wear a helmet"). The consequences of breaking the first
type of rule are social, the second physical.
R.M. was as good as control subjects at spotting when
a precautionary rule was broken. But for social rules,
he was 30 per cent worse at spotting cheats.
"Cheater detection in the brain is a separate system
from reasoning in other domains," comments Pascal Boyer,
an anthropologist and psychologist at Washington
University in St Louis, Missouri.
"There's probably room in the brain for a list of
modes of social interaction," says neuroscientist Steven
Pinker of the Massachusetts Institute of Technology,
Cambridge. This list might include guessing others'
social status or sexual desires.
Specialized, evolved cheat detection should be
present in humans regardless of their culture. To test
this, the team took their experiment to the Shiwiar
people of the Ecuadorian Amazon.
These hunter-horticulturalists were isolated from the
outside world until the late 1970s. But they can spot
when someone breaks a deal as well as anybody, getting
it right more than 80 per cent of the time.
"A stockbroker in New York and a hunter in an
Amazonian village will probably have to activate the
capacity [to detect cheats] in different ways," comments
Boyer. "But the capacity is there, ready to be
All social primates, such as Rhesus monkeys and
chimpanzees, recognize social exchange and cheaters, so
the adaptation may be evolutionarily quite old.