Partial reinforcement in serial autoshaping: The role of attentional and associative factors

In Experiment 1, pigeons were autoshaped to two stimuli (A and B) each followed by delayed reinforcement on 50% of trials. A different stimulus (X) was presented in the interval between stimulus A and reinforcement (A-X-US) and not when stimulus A was nonreinforced (A---). The X stimulus was also presented following the stimulus B trials that were nonreinforced (B-X) and was absent when stimulus B was reinforced (B---US). Not only was the response rate to A higher, but so was the rate in the intervals immediately following A, whether or not these intervals contained X. This latter finding is inconsistent with the interpretation that pigeons discriminated between X when it followed A and when it followed B and leaves open the possibility that X acts as a “catalyst”. The same general design was employed in Experiment 2 as was used in Experiment 1 with the exception that the catalytic function of X was equated for A and B by presenting reinforcement on B-X trials. The A stimulus, however, still generated the higher response rate. A new interpretation is offered that suggests that variable reward magnitude will maintain attention to a stimulus and that attention will generate keypecking.