Latencies to first food pulling of focal rats for their previously cooperating partner vs. for their previously defecting partner. The previous helpfulness of the partner influenced the latency (in seconds) of test subjects to provide the first food reward to its partner. Every data point represents the focal individual’s latency to the first food provisioning of the cooperating partner compared with that of the defecting partner. Data points above the dashed line represent focal individuals who pulled earlier for the cooperating partner than for the defecting partner. This is inversed for data points below the dashed line. Significantly more focal individuals pulled earlier for their cooperating partner than for the defecting partner.