#Reciprocity

A new study shows that when rats engage in reciprocal cooperation, a surge of oxytocin in the orbitofrontal cortex not only underpins fair give-and-take but also enhances their empathy toward a partner. The researchers designed an automated “pay-first, reward-later” task in which two rats must coordinate by each triggering the other’s reward within a tight time window. Over time, the pair’s cooperation became direct reciprocity rather than mere mutual benefit, and richer social interactions predicted faster, more reliable cooperation. Crucially, oxytocin release in the orbitofrontal cortex was significantly higher during reciprocity than during simple mutualism or solitary tasks. In contrast, rats genetically modified to lack oxytocin signaling showed more free-riding, were less likely to reciprocate after betrayal, and did not exhibit the same empathy boost that wild-type animals displayed when paired with cooperative partners.