Adrenal Hypertrophy in the Rat as a Function of Probability and Frequency of Punishment

Abstract

After training on a regular reinforcement procedure in which a lever-pressing response produced milk reward, each of 16 groups of water-deprived rats was exposed to a different concurrent contingency of regular reinforcement and random interval punishment for 20 experimental sessions. Under the intermittent punishment schedules used, the programmed probability and frequency of response-contingent electric shock were independently manipulated. Autopsies revealed (a) that changes in adrenal weights were about the same (independent of the amount of shock) over a wide range of punishment frequencies and (b) that the amount of adrenal hypertrophy was a decreasing function of shock probability over a range of probabilities from 0.0625 to 1.00.