Retention of context blocking in taste-aversion learning.

A series of experiments examined recovery from context blocking across a retention interval. In two flavor-aversion studies, rats received 0, 2, or 4 context + US pairings in Phase 1, a flavor + US pairing in Phase 2, and flavor testing after a 3-day or a 14-day retention interval. The procedures in Experimental 1 were performed in a novel context, whereas Experiment 2 was conducted in a moderately familiar context. In Experiment 1, the effects of 2 context + US pairing dissipated over the retention interval (i.e., the taste aversion increased in strength), but the effects of 4 context + US pairings did not change. In Experiment 2, no context blocking was observed after 2 context + US pairings, but the effects of 4 context + US pairings decreased across the retention interval. These studies are the first to show recovery from context blocking across a retention interval following single-element conditioning. Furthermore, Experiment 3 demonstrated that extinction of the context prior to taste conditioning eliminated context blocking, and Experiment 4 showed that weak taste aversions do not increase in strength across a retention interval. It is proposed that forgetting of the context-US association across an extended retention interval is the mechanism underlying recovery from context blocking.