THE ROLE OF US NOVELTY IN RETENTION INTERVAL EFFECTS IN SINGLE-ELEMENT TASTE-AVERSION LEARNING

Retention interval effects are seen in taste-aversion learning when si ngle-element aversions are significantly weaker 24 h after conditionin g compared with tests at later intervals. This report contains three e xperiments which suggest that the source of the increased drinking at the 1-day interval is nonassociative interference produced by the nove l conditioning episode. In Experiment 1, a parametric analysis demonst rated that aversion strength increased monotonically over a 30-h perio d following conditioning, and that by 48 h after conditioning it was s tabilized. In Experiment 2, a single US preexposure was used to reduce the novelty of the US prior to conditioning. As a result, animals pre exposed to the US had stronger taste aversions than did non-preexposed controls at a 1-day retention interval; however, no differences were seen at a 5-day interval. Experiment 3 investigated whether the counte rintuitive outcome of Experiment 2 was due to the summation of environ ment-illness and taste-illness associations at the 1-day test. The res ults ruled out the summation argument; the US preexposure did not need to be presented in the conditioning context to strengthen the aversio n at the 1-day interval. Collectively, these results suggest that the presentation of a surprising US can interfere with the retrieval of th e taste-illness association for a short period after conditioning, and that this contributes to the retention interval effect.