Monkeys keep count of niceties and selfless behavior in a part of their brain.
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.
The researchers found that in two out of the three brain areas being recorded, neurons fired in the presence or absence of the juice reward only. By contrast, the third area — known as the anterior cingulate gyrus — responded only when the monkey allocated the juice to the neighbour and observed it being received. The authors suggest the neurons in the ACG respond to and record the act simultaneously. The study’s results are published today in Nature Neuroscience.