SCIENCE & TECHNOLOGY
Animal behaviour
Fair and square
EVERYBODY loves a fat pay rise. Yet pleasure at your own can vanish if you
learn that a colleague has been given a bigger one. Indeed, if he has a reputation
for slacking, you might even be outraged. Such behaviour is regarded as ?all too
human?, with the underlying assumption that other animals would not be capable of
this finely developed sense of [id:9189] . But a study by Sarah Brosnan and Frans de
Waal of Emory University in Atlanta, Georgia, which has just been published in
Nature, suggests that it is all too monkey, as well.
The researchers studied the behaviour of female brown capuchin monkeys, which
have all the necessary ingredients to capture the public imagination. They look
cute. They are good-natured, co-operative creatures, and they share their food
readily. [id:9190] , like their female human counterparts, they tend to pay much closer
attention to the value of ?goods and services? than males (although why this is so
remains a mystery).
Such characteristics make them perfect candidates for Dr Brosnan?s and Dr de
Waal?s study. The researchers spent two years teaching their monkeys to exchange
tokens for food. Normally, the monkeys were happy enough to swap pieces of rock
for slices of cucumber. However, when two monkeys were placed in separate but
adjoining chambers, so that each could observe what the other was getting in
return for its rock, their behaviour became markedly different.
In the world of capuchins, grapes are luxury goods (and much preferable to
cucumbers). So when one monkey was handed a grape in exchange for her token,
the second was [id:9191] to hand hers over for a mere piece of cucumber. And if one
received a grape without having to provide her token in exchange at all, the other
tossed her own token at the researcher or out of the chamber. Indeed, the mere
presence of a grape in the other chamber (in the absence of an actual monkey able
to eat it) was enough to arouse [id:9192] behaviour in a female capuchin.
Dr Brosnan and Dr de Waal report that such behaviour is unusual in their trained
monkeys. During two years prior to these experiments, failure to exchange tokens
for food occurred in fewer than 5% of trials. And what made the behaviour even
more [id:9193] was that these monkeys forfeited food that they could see ? and
which they would have readily accepted in almost any other set of circumstances.
The researchers suggest that capuchin monkeys, like humans, are guided by
[id:9194] . In the wild, they are a co-operative, group-living species. Such
cooperation is likely to be stable only when each animal feels it is not being
cheated. Refusing a lesser reward signals feelings of indignation to other members
of the group.
So it seems that such feelings are not the preserve of [id:9195] alone. However,
whether such a sense of fairness evolved independently in capuchins and humans,
or whether it stems from the common ancestor that the species had 35m years ago,
is, as yet, an unanswered question.
The Economist