New York: Researchers have found brain cells in monkeys that fire only when the creatures act unselfishly, and which may provide clues to the neural basis of altruism in humans.
Researchers said the cells fire in rhesus monkeys when they gave juice away, but not when they received it.
The findings may shed light on why many animals, including humans, exhibit kind, unselfish behaviour that doesn`t directly benefit them, `LiveScience` reported.
The new findings provide a "complete picture of the neuronal activity underlying a key aspect of social cognition. It is definitely a major achievement," said Matthew Rushworth, a neuroscientist at Oxford.
Why animals act unselfishly has been a longstanding mystery. This primitive do-gooder impulse in animals may have evolved into the altruism we see in humans today, said study co-author Michael Platt, a neuroscientist at Duke University.
Platt and his colleagues taught rhesus monkeys to play a simple computer game where they looked at different shapes to either give themselves, a nearby neighbour monkey, or nobody a squirt of juice.
Unsurprisingly, monkeys almost always give themselves juice when they have the option.
Researchers then set up another trial where they could either give the other monkey juice or give it nothing. None of the choices led to a tasty juice squirt for the actor monkey.
During the trials, electrodes in the monkey`s brain recorded the electrical firing from neurons in brain regions suspected of playing a role in altruism. The monkeys consistently preferred doling out juice to other monkeys over giving nothing.
When the researchers replaced the second monkey with another bottle of juice, the monkeys showed no preference for dispensing juice, showing that they were motivated by the reward to the other monkey.
A brain region called the orbitofrontal cortex, which is known to play a role in reward processing, fired when monkeys got juice squirts for themselves.
"The orbitofrontal cortex seems to be all about your personal reward. It`s egocentric," Platt said.