Abstract: | In Experiment 1, pigeons exposed to US ONLY pretraining were observed to be retarded in the acquisition of autoshaping relative to naive controls; however, gross changes in contextual stimuli between pretraining and testing alleviated the retardation effect. In Experiment 2, groups of pigeons exposed to CS ONLY, US ONLY, or random CS-US presentations (TRC) were tested for the acquisition of autoshaping. The US ONLY and TRC groups were retarded relative to naive controls. The context change manipulation eliminated the US ONLY retardation effect and attenuated, but did not eliminate, the TRC retardation effect. Context blocking accounts for the US ONLY effect and contributes to the TRC effect; however, context-independent retardation following TRC pretraining suggests the operation of the learned irrelevance cognition. |