Gastric ulcers in the rat as a function of the temporal relationship between punishment and reward.

This experiment investigated the effectiveness of four conflict situations in inducing stomach lesions in rats. The four conflict situations differed in that shock was made contingent to responses which varied in their temporal proximity to the consummatory response. Using an operant leverpressing response, rewarded by food on a VI 2-minute schedule, grid shock was presented either: (a) after a nonrewarded lever response, (b) after a response which produced a food pellet, (c) after the rat collected the food pellet, or (d) while the rat was eating the pellet reward. Animals shocked while eating the food reward demonstrated the highest incidence of stomach lesions, whereas animals shocked while performing the barpressing operant response did not differ from controls in incidence of ulcer.