Civil society may hinge on a tiny piece of
tissue at the front of the human brain, a
new study suggests.
Experiments involving
a "fairness" game show that the
right side of this region -- called the dorsolateral
prefrontal cortex -- helps people suppress
selfish urges in obviously unjust situations,
even at their own expense.
When researchers used a mild electric current
to temporarily short-circuit this area, the
law of the jungle quickly reasserted itself.
People with disabled right-side dorsolateral
prefrontal cortexes grabbed whatever money
they could from lopsided transactions -- even
when they knew the deal they were getting
was grossly unfair.
"They understood the unfairness of it
all, but they simply couldn't inhibit their
need for getting the money," said Paul
Sanberg, director of the Center of Excellence
for Aging and Brain Repair at the University
of South Florida College of Medicine in Tampa.
Sanberg was not involved in the study, which
is published in the Oct. 6 issue of Science.
The Swiss and American team behind this research
noted that, despite a long history of crime,
wars and rapaciousness, human beings are innately
cooperative. In fact, Homo sapiens
is the only species to exhibit "reciprocal
fairness" -- the punishment of others'
unfair behaviors, even in situations where
doing so hurts the punisher.
This behavior is demonstrated in an oft-used
tool in behavioral science called the "Ultimatum
Game."
In this game, one player is given a set amount
of money. He is then instructed to hand over,
at his own discretion, a share of the money
to a second player.
Player 2 can either accept the amount offered
or refuse the deal altogether, in which case
both players receive no money.
When Player 1's offer is very low -- for
example, $2 out of a total of $20 -- it would
still behoove Player 2 to accept the offer,
since $2 is better than nothing.
However, under normal circumstances, participants
put in this position in the game overwhelming
refuse such low offers, which they perceive
as grossly unfair. Instead, they forfeit their
own self-interest so they can "punish"
Player 1.
Why might this be so? Humans are highly socially
evolved, and punishing unfairness "helps
sustain cooperation in groups," said
study lead researcher Ernst Fehr, director
of the Institute for Empirical Research in
Economics at the University of Zurich.
Because more cohesive groups tend to have
better survival prospects, humans who suppress
their immediate urges end up on the "winning
team," evolutionarily speaking.
Fehr's group sought to find the seat of this
selfishness-override in the brain.
In prior brain-imaging studies, the dorsolateral
prefrontal cortex (DLPFC) lit up during the
game, so the researchers focused there.
In the study, they had participants play
the game under two conditions. In the first
condition, the researchers passed a mild electric
current through the right or left hemispheres
of Player 2's DLPFC, temporarily deactivating
these brain regions. Other participants took
on the Player 2 role under sham conditions
where no real electric current was flowing.
"The big surprise," Fehr said,
"is that a relatively minor inhibition
of the right DLPFC removes or weakens
the subject's ability to override their self-interest."
Players whose right-side DLPFC's were "switched
off" accepted even very low amounts of
cash nearly half (45 percent) of the time
-- even though they knew the offer was terribly
unfair.
But under normal conditions, barely one
in 10 players accepted such insulting low
offers, the researchers found.
The experiment shows that this part of the
cortex "is clearly very important for
our social behavior, our societal evolution,"
Sanberg said. The right side of the DLPFC
helps people resist those strong urges for
sex, money and general acquisitiveness that
come from more primitive sites outside the
cortex, he said.
"It provides modulation of those urges,
so that you can have control over them,"
Sanberg added. "As we evolved, we somehow
developed this control over our basic needs."
One intriguing line of research is whether
the right-side DLPFC functions similarly in
everyone -- even hardened criminals or sociopaths.
"This is a very interesting question
which we are just exploring now," Fehr
said. "Preliminary results suggest that
the right DLPFC has very different activation
across individuals."
His team also noticed that the left
side of the DLPFC also sprang to life during
the game, although its role remains much more
mysterious. "We are just in the process
of studying this now," Fehr said.
