Eight isopods, Porcellio scaber, were trained with water reinforcement to turn in a T-maze to criterion of correct responses. They were then tested through nine reversals of the turning response. An analysis of variance indicated that mean errors to criterion declined significantly over reversals (F = 4.78, d.f. = 9/63, P < .001).

Four isopods, Porcellio scaber, were subjected to a water-deprivation procedure in a temperature-and humidity-controlled environment. Ss were then given trials in a T maze. When turning against a pre-established preference (correct turn) was followed by access to water, all Ss began o n subsequent trials to turn against preference to a criterion of 9 correct rurns out of 1 0 consecutive trials, within a range of 1 0 to 44 trials. A control group not given access to water after turning did not exhibit any marked change in turning tendency.