The #1 source for news about monkeys and apes

[Josh Greenman <joshg1973 AT yahoo.com>]

http://www.lasvegassun.com/sunbin/stories/nat-gen/2003/sep/17/091702689.html

Today: September 17, 2003 at 10:04:08 PDT 

Study Shows Monkeys May Resent Unfairness
By ALEX DOMINGUEZ
ASSOCIATED PRESS 



Humans aren't the only ones who hate a bum deal, it turns out. 

In a recent study, brown capuchin monkeys trained to exchange a granite token 
for a
cucumber treat often refused the swap if they saw another monkey get a better 
payoff - a
grape. 

Instead, they often threw the token, refused to eat the piece of cucumber, or 
even gave
it to the other capuchin after viewing the lopsided deal, said Emory 
University
researcher Sarah Brosnan. 

She said the results indicate man and monkey may have inherited a sense of 
fairness from
an evolutionary ancestor. 

"This implies we evolved this way," said Brosnan, whose work with colleague 
Frans B.M. de
Waal is reported in Thursday's issue of the journal Nature. 

The trait may have helped species cooperate and survive, Brosnan said. 

However, Charles Janson, who studies capuchins at the State University of New 
York at
Stony Brook and was not involved in the research, suggested the monkeys' 
behavior may
have been learned in captivity, rather than inherited as an evolutionary 
adaptation. 

Brosnan said she doubted the behavior was learned, saying most animals 
"cannot learn
things which they do not naturally do in the wild." 

"More importantly, however, learning behavior requires that individuals get 
rewarded for
performing a specific behavior," Brosnan said. "In our test, the subject 
actually
received less reward for refusing to exchange." 

The researchers, at Emory's Yerkes National Primate Research Center, studied 
five female
monkeys, testing them two at a time. 

When both monkeys were given a cucumber slice after handing over the token, 
they
completed the trade 95 percent of the time. 

But when one was given the tastier grape for the same amount of work, the 
rate of
cooperation from the other monkey fell to 60 percent, with the cheated 
primate sometimes
throwing the token, refusing the cucumber or giving the cucumber to the other 
monkey. And
when one didn't have to do anything to get a grape, the other made the trade 
for the
cucumber only 20 percent of the time. 

The refusal to make the exchange increased as the experiment went on, the 
researchers
reported. 

"They were not happy with me," Brosnan said, although she later added that 
she couldn't
really know what the monkeys' emotions were. 

The scientists concluded that capuchins apparently measure rewards in 
relative terms,
comparing their rewards to those available, as well as their efforts to those 
of others. 

Small and highly animated with faces that resemble wizened old men, the 
tropical
forest-dwelling capuchins were chosen for the experiment because they often 
share food. 

Brosnan, who said she is now conducting similar studies with chimpanzees, 
noted that the
capuchin that got the grape didn't react at all to the unjustness of the 
situation. That
"probably implies there is still a lot of difference between their sense of 
fairness and
ours," she said.