Jones, B. M., & Davison, M. (1997).
The control of choice by its consequences.
Journal of the Experimental Analysis of Behavior,
68, 329-348.
Five pigeons were trained on concurrent variable-interval
schedules in which equal rates of reinforcement were always
arranged for left- and right-key responses, but different overall
rates were signaled by key colors. Sessions began with both keys
lit yellow for the instrumental phase. If, after 20 s of this
phase, the relative number of responses that had been made to the
left key equaled or exceeded .75, both keys changed red for the
contingent phase. The contingent phase arranged another
concurrent variable-interval schedule for a further 20 s before
the instrumental phase was reinstated. However, if preference in
the instrumental phase did not exceed .75, the instrumental phase
continued for a further 20 s before preference was again compared
with the criterion. In Part 1, the reinforcer rate arranged in
the instrumental phase was held constant at 4.8 reinforcers per
minute, while the reinforcer rate arranged in the contingent
phase was varied across conditions from 0 to 19.2 over five
steps. In Part 2, reinforcer rates in the contingent phase were
kept constant at 36 per minute, while reinforcer rates in the
instrumental phase were varied from 0 to 36 over seven steps.
Part 3 replicated Part 2 but used reinforcer rates in both phases
that were one third of those arranged in Part 2. Measures of
choice obtained by summing responses across presentations of the
instrumental phase became more extreme toward the left key as the
reinforcer rate obtained in the contingent phase was increased
(Part 1) and as the reinforcer rate obtained in the instrumental
phase was decreased (Parts 2 and 3). Changes in these measures of
choice were accompanied by systematic changes in the relative
frequency with which the criterion was exceeded. Changes in both
these measures were correlated with changes in the relative
frequency with which subjects responded exclusively to the left
key. These results are discussed with respect to the two choices
that were concurrently available in this procedure and the
response alternatives that might constitute the concurrent
operants in each choice.
Key words: choice, concurrent variable-interval schedules,
reinforcer rates, behavioral units, pecking, pigeons