Forgetting of Acquisition and Extinction in an Invertebrate.

Two experiments with isopods, Armadillidium vulgare, were reported. In Experiment I, two groups of five Ss each learned to run a T maze to escape light and heat. Both original learning (OL), and relearning (RL) the next day, were to a criterion 9/10 correct. Between OL and RL one group was immobilized (I), and the other group was given the opportunity for activity (A). The I treatment resulted in greater savings on RL than did the A treatment, and it was thus concluded that A is a retroaction treatment. Experiment II was like I except that all Ss were extinguished immediately following OL, and then given either A or I until RL. In this experiment, the A treatment led to no savings, but the I treatment produced negative savings (more trials on RL relative to OL). It was concluded that the A treatment had retroactively interfered with extinction, and this result was discussed as analogous to differential spontaneous recovery in favor of the A group. It was concluded that Liberman's (4, 5) theory (that spontaneous recovery is due to the forgetting of extinction) is supported by the result of Experiment II.