Monkeys might not be known for their generosity, but when they do seem to act selflessly, a specific area in their brains keeps track of these kindnesses.
The discovery of this neuronal tally chart may help scientists to understand the neural mechanisms underlying normal social behaviour in primates and humans, and might even provide insight into disorders such as autism, in which social processing is disrupted.
Steve Chang and his colleagues from Duke University in Durham, North Carolina, used electrodes to directly record neuronal activity in three areas of the brain prefrontal cortex that are known to be involved in social decision-making, while monkeys performed reward-related tasks.
When given the option either to drink juice from a tube themselves or to give the juice away to a neighbour, the test monkeys would mostly keep the drink. But when the choice was between giving the juice to the neighbour or neither monkey receiving it, the choosing monkey would frequently opt to give the drink to the other monkey.