Concurrent variable‐interval variable‐ratio schedules in a dynamic choice environment
In fast-changing mixed schedules, time allocation still rules choice even when one side demands a set number of responses.
01Research in Context
What this study did
Bell and colleagues mixed two kinds of reinforcement schedules. One side paid off after a set amount of time (VI). The other side paid off after a set number of responses (VR).
The values changed every two seconds. Pigeons had to keep track of which side was currently richer.
What they found
Even though one schedule required fast pecking, the birds acted as if both sides were time-based. They spent most of their time on the richer alternative and only briefly sampled the lean one.
Response rate did not decide preference; time spent did.
How this fits with other research
Burgess et al. (1971) saw heavy switching when two VR schedules ran together. Bell’s birds switched less because the VI side removed the need to peck quickly.
Bensemann et al. (2015) showed that steady VI schedules follow the constant-ratio rule. Bell’s fast-flipping VI/VR mix still followed the same rule, hinting that the rule holds even when contingencies spin every two seconds.
Van Houten et al. (1980) moved VR from pigeons to deaf students using token boards. Their VR tokens calmed disruption and lifted attention. Bell’s lab result backs that clinical move: VR can be blended with time-based pay-offs without confusing the learner.
Why it matters
When you mix time-based and response-based pay-offs, watch where the learner hangs out, not how fast they respond. If you run a token board or DRO plus a response requirement, quick schedule flips should still work. Start by tracking time allocation across alternatives; it will tell you preference sooner than counting responses.
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02At a glance
03Original abstract
Most studies of operant choice have focused on presenting subjects with a fixed pair of schedules across many experimental sessions. Using these methods, studies of concurrent variable- interval variable-ratio schedules helped to evaluate theories of choice. More recently, a growing literature has focused on dynamic choice behavior. Those dynamic choice studies have analyzed behavior on a number of different time scales using concurrent variable-interval schedules. Following the dynamic choice approach, the present experiment examined performance on concurrent variable-interval variable-ratio schedules in a rapidly changing environment. Our objectives were to compare performance on concurrent variable-interval variable-ratio schedules with extant data on concurrent variable-interval variable-interval schedules using a dynamic choice procedure and to extend earlier work on concurrent variable-interval variable-ratio schedules. We analyzed performances at different time scales, finding strong similarities between concurrent variable-interval variable-interval and concurrent variable-interval variable- ratio performance within dynamic choice procedures. Time-based measures revealed almost identical performance in the two procedures compared with response-based measures, supporting the view that choice is best understood as time allocation. Performance at the smaller time scale of visits accorded with the tendency seen in earlier research toward developing a pattern of strong preference for and long visits to the richer alternative paired with brief "samples" at the leaner alternative ("fix and sample").
Journal of the Experimental Analysis of Behavior, 2017 · doi:10.1002/jeab.286