Stimulus and procedural determinants of the forgetting of conditioned fear.

Two studies investigated factors believed to influence the retention of acquired fear in rats. The results show clearly that the lack of forgetting over 24-hr interval reported by previous investigators is due to a depression of performance on the immediate test (3-min retention interval) resulting from the procedure of not handling the rats during conditioning but then handling them on every trial during the retention test. In accord with the McAllister's interpretation of related results, the depression of performance after short retention intervals may be due to a lack of generalization from training to the testing situation. As the retention interval is lengthened, the amount of generalization increases and escape performance improves on a relative basis. The nature of the retention function may be severely distorted by selection of an inappropriate paradigm for its evaluation.