Choice Behavior in Transition: Development of Preference for the Higher Probability of Reinforcement

Abstract

Ten acquisition curves were obtained from each of 4 pigeons in a two-choice discrete-trial procedure. In each of these 10 conditions, the two response keys initially had equal probabilities of reinforcement, and subjects' choice responses were about equally divided between the two keys. Then the reinforcement probabilities were changed so that one key had a higher probability of reinforcement (the left key in half of the conditions and the right key in the other half), and in nearly every case the subjects developed a preference for this key. The rate of acquisition of preference for this key was faster when the ratio of the two reinforcement probabilities was higher. For instance, acquisition of preference was faster in conditions with reinforcement probabilities of .12 and .02 than in conditions with reinforcement probabilities of .40 and .30, even though the pairs of probabilities differed by .10 in both cases. These results were used to evaluate the predictions of some theories of transitional behavior in choice situations. A trial-by-trial analysis of individual responses and reinforcers suggested that reinforcement had both short-term and long-term effects on choice. The short-term effect was an increased probability of returning to the same key on the one or two trials following a reinforcer. The long-term effect was a gradual increase in the proportion of responses on the key with the higher probability of reinforcement, an increase that usually continued for several hundred trials.

Choice behavior in transition: Development of preference in a free-operant procedure

“…The original version of melioration theory (Herrnstein & Vaughan, 1980) predicts identical acquisition rates for all conditions with the same difference 00-tween reinforcement probabilities (4)1 -4>2)' Thus, none of these theories predicts the pattern of results obtained by Bailey and Mazur. However, a more recent version of melioration theory (Vaughan, 1985) is much more general in its form, and this version makes no specific predictions about this matter. Bailey and Mazur (1990) showed that their results were consistent with an analysis based on Weber's law. Weber's law states that for any stimulus dimension (probability of reinforcement in this case), two stimuli will 00 more discriminable ifthey differ by a larger percentage.…”

“…Bailey and Mazur (1990) obtained one acquisition curve from each pigeon subject in each condition of their experiment. Every condition began with a few one-probability sessions, which were followed by one transition session and then several two-probability sessions, In the oneprobability sessions, a single reinforcement schedule assigned reinforcers to either of two response keys, with…”

“…In brief, each condition began with sessions in whichresponse proportions were about equal on the two keys; then the development of preference was observed when the probability of reinforcement became higher on one key. Bailey and Mazur (1990) varied the values of 4>1 and 4>2 across conditions to deterrnine how different pairs of reinforcement probabilities would affect the rate of acquisition. In particular, they used four different pairs of reinforcement probabilities in which the difference 4>1 -4>2 was the same, but the ratio 4>1/4>2 was different.…”

“…The present experiment used a procedure similar to that of Bailey and Mazur (1990), except that a free-operant procedure was used. This was done both to examine the applicability of the Weber's law hypothesis to the freeoperant case and to test the predictions ofMyerson's kinetic model.…”

“…The procedure of this experiment differed from that of Bailey and Mazur (1990) in several other ways. Because there were no ITIs, each session could inc1ude more responses, and sessions ended after 1,000 or 1, 100 responses, as compared with 600 responses in the Bailey and Mazur experiment.…”