MOLECULAR CONTINGENCIES: REINFORCEMENT PROBABILITY 1

Abstract

Pigeons obtained food by responding in a discrete‐trials two‐choice probability‐learning experiment involving temporal stimuli. A given response alternative, a left‐ or right‐key peck, had 11 associated reinforcement probabilities within each session. Reinforcement probability for a choice was an increasing or a decreasing function of the time interval immediately preceding the choice. The 11 equiprobable temporal stimuli ranged from 1 to 11 sec in 1‐sec classes. Preference tended to deviate from probability matching in the direction of maximizing; i.e. , the percentage of choices of the preferred response alternative tended to exceed the probability of reinforcement for that alternative. This result was qualitatively consistent with probability‐learning experiments using visual stimuli. The result is consistent with a molecular analysis of operant behavior and poses a difficulty for molar theories holding that local variations in reinforcement probability may safely be disregarded in the analysis of behavior maintained by operant paradigms.