Effects of reinforcer probability on attending to element and compound sample stimuli

Previous research has shown that divided-attention performance is sensitive to variations in relative reinforcement in a manner consistent with the generalized matching law. Two experiments with pigeons were designed to better understand the effects of different reinforcement conditions on divided-attention performance. Experiment 1 asked whether separate experience with different relative reinforcement probabilities for elements alone would produce changes in performance during nondifferentially reinforced divided-attention trials with compound samples consisting of those elements. The results suggest that accuracy following compound sample trials varied as a function of relative reinforcement experienced in element trials in a manner consistent with the matching law. Experiment 2 used an adjusting-sample-duration procedure to maintain constant accuracy on element and divided-attention trials and varied the probability of reinforcement across conditions. The sample durations that were required to maintain constant accuracy increased as reinforcement probability decreased even though that longer sample durations were required to maintain accuracy for compound-sample trials than for element-sample trials (the element-superiority effect). Overall, the present results are consistent with the notion that increased attention is allocated to stimuli that are associated with more reinforcement.