Behavioral contrast as a function of the temporal location of reinforcement.
Reinforcer timing inside an FI can reverse the direction of behavioral contrast in the next component.
01Research in Context
What this study did
The team ran a multiple schedule with two VI parts and one FI part. They moved the single food delivery to the start, middle, or end of the FI.
Pigeons pecked a key for grain. The only change was when the reinforcer arrived inside the FI.
What they found
Food at the middle or end of the FI made responding in the other VI part speed up. Food at the very start of the FI made that same VI responding slow down.
The switch to a low-rate stretch right after the reinforcer seemed to drive the effect.
How this fits with other research
Jensen et al. (1973) showed that leaving food out in one part can also create contrast. Cicerone (1976) adds that even when food is given, its timing inside the part can flip the direction.
Sturmey (1995) later found that shorter parts make any contrast bigger. If you run brief components, expect the timing effect A found to show up stronger.
Innis (1978) saw quick, minute-by-minute contrast inside FIs. Cicerone (1976) explains one reason: the reinforcer’s place sets up the rate drop that follows.
Why it matters
When you set up a mixed schedule in practice, think about where the reinforcer sits in each part. Placing it early can suppress, not boost, responding elsewhere. If you see surprise drops in adaptive work after a rich patch, try shifting the reward moment later in the cycle.
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Join Free →Slide the reinforcer one-third later into the lean component and watch if skill bursts return in the other part.
02At a glance
03Original abstract
Pigeons were trained on a multiple variable-interval variable-interval schedule of reinforcement. One component was then changed to a variation of a fixed-interval schedule in which the same rate of reinforcement was obtained as previously but the location of the reinforcer was fixed within the component. The effects of different temporal locations were compared. An increase in response rate for the unchanged variable-interval component (behavioral contrast) occurred when the reinforcer was located in the middle or at the end of the FI component, but response suppression occurred when it was located at the beginning of the component. The pattern of results cannot be explained by any previous theories of contrast. The overall response rates, and the pattern of local rates within the components, were consistent with the hypothesis that the major determinant of the contrast effect was the transition to a lower reinforcement rate following the unchanged component.
Journal of the experimental analysis of behavior, 1976 · doi:10.1901/jeab.1976.26-57