Avoidance of risk as a determinant of cooperation.

Pairs of subjects could either cooperate or respond on a lower paying individual task. Whenever both subjects chose to cooperate, either subject could make a response that took $1.00 of the other's earnings. In Exp. I, a stimulus signalled when a "take" response had been made. Either subject could avoid the loss by switching to the individual task within 5 sec after the stimulus appeared. Rates of cooperation were high when losses could be avoided but decreased again when the avoidance condition was removed. In Exp. II, a response prevented "takes" from occurring for a specified time interval after the response. This procedure also maintained cooperation. When each avoidance response subtracted from earnings, both avoidance responding and cooperation were eliminated.