[monkeywire] Experiment Proves Existence of Monkey Justice

Amber Hewins ahewins at mac.com
Sun Sep 23 10:25:19 EDT 2007


http://news.bbc.co.uk/2/low/science/nature/3116678.stm
BBC NEWS / SCIENCE/NATURE


Wednesday, 17 September, 2003, 18:39 GMT 19:39 UK
Monkeys show sense of justice
By Dr David Whitehouse
BBC News Online science editor

Monkeys have a sense of justice. They will protest if they see  
another monkey get paid more for the same task.

Monkeys display sense of justice Researchers taught brown capuchin  
monkeys to swap tokens for food. Usually they were happy to exchange  
this "money" for cucumber.

But if they saw another monkey getting a grape - a more-liked food -  
they took offence. Some refused to work, others took the food and  
refused to eat it.

Scientists say this work suggests that human's sense of justice is  
inherited and not a social construct.

Differential reward experiment

The research was carried out at Emory University in the US, by Sarah  
Brosnan and Frans de Waal, and is reported in the journal Nature.

"I'm extremely interested in the evolution of cooperation," Sarah  
Brosnan told BBC News Online.

"One of the most interesting areas is the recent suggestion that  
human cooperation is made more effective by a sense of fairness."

She wanted to find out if the human sense of fairness is an evolved  
behaviour or a cultural construct - the result of society's rules.

So she and her colleagues devised an experiment using capuchin monkeys.

Experiment, Nature/Emory University Sarah Brosnan said: "I chose the  
capuchin because they are very cooperative, and because they come  
from a very tolerant society.

"We designed a very simple experiment to see whether or not they  
react to differential rewards and efforts."

Capuchins like cucumber, but they like grapes even more. So a system  
was devised whereby pairs of capuchins were treated differently after  
completing the same task.

"They had never before been in any sort of situation where they were  
differentially rewarded," she said.

"We put pairs of capuchins side by side and one of them would get the  
cucumber as a reward for a task."

The partner sometimes got the same food reward but on other occasions  
got a grape, sometimes without even having to work for it."

'A highly unusual behaviour'

The response was dramatic, the researchers said.

"We were looking for a very objective reaction and we got one. They  
typically refused the task they were set," Sarah Brosnan said.

"The other half of the time they would complete the task but wouldn't  
take the reward. That is a highly unusual behaviour.

"Sometimes they ignored the reward, sometimes they took it and threw  
it down," she added.

Nature/Emory University The researchers were not surprised that the  
monkeys showed a sense of fairness, but they were taken aback that  
they would turn down an otherwise acceptable reward.

"They never showed a reaction against their partner, they never  
blamed them," Sarah Brosnan said.

Commenting on the results, experts in the subject told BBC News  
Online that the idea of a long evolutionary history for a sense of  
fairness was an exciting one.

However, they added that they would like to see more research  
involving more than just the five subjects tested in the Nature study.

So does our instinctive feeling of fairness predate our species?

"It may well," Sarah Brosnan said, and further experiments are  
planned to see how extensive a sense of justice in the animal world is.

"We are currently repeating the study on chimpanzees, a great ape  
species, to learn something more about the evolutionary development  
of the sense of fairness.

"I suspect that there are other non-primate species with tolerant  
societies that will show the same behaviour." 


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