Variable-time reinforcement in multiple and concurrent schedules.
Behavioral contrast only appears when the altered component truly loses value, not just response opportunity.
01Research in Context
What this study did
Clopton (1972) worked with pigeons in a two-key box. The birds pecked for food on variable-interval schedules.
The team swapped one key from normal payoff to two new rules: extinction (no food) or free food every 30 seconds no matter what. They watched how this change altered pecking on the other, unchanged key.
What they found
When the first key went to extinction, the second key showed classic behavioral contrast: more pecks, faster rate.
When the first key paid free food, contrast vanished. Birds kept the same steady pace on the second key. The result says contrast is about value shifts, not just lower response rates.
How this fits with other research
Hineline et al. (1969) saw the same boost when extinction followed a rich schedule, but they never tested free food. Clopton (1972) adds the missing piece: free food kills the boost, so value, not rate, drives the effect.
de Rose (1986) later showed longer extinction makes the boost bigger. That lines up with M: more value loss in one spot means more gain in the other.
Delaney et al. (1998) offered a theory: less food means less habituation, so the leftover food feels richer. M’s free-food data fit neatly—steady food keeps habituation high and contrast low.
Why it matters
When you run multiple schedules with clients—work first, play second—remember that taking reinforcement away is not enough to create contrast. You must also guard against accidental free reinforcement (like attention or edibles given on a timer). If the value stays equal across components, you will not see the surge you want in the target skill.
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Join Free →Before starting a contrast-based intervention, remove any response-independent reinforcers (timer-based praise, free snacks) from the low-demand component.
02At a glance
03Original abstract
Experiment I examined the role of a reduced rate of responding in the occurrence of behavioral contrast. Four rats and a pigeon were exposed to a two-component multiple schedule in which one component was always a variable-interval schedule. The second component was, at different times, either a variable-time schedule in which food was delivered independently of responding, or extinction. Both extinction and the variable-time schedule reduced the rate of responding in the second component. Behavioral contrast was observed, however, only when extinction was scheduled in the second component. Experiment II examined preference, as measured by time allocation in concurrent schedules for a variable-interval schedule relative to a variable-time schedule. Two rats displayed a lack of preference between the two schedules. The results of these experiments support a preference interpretation of behavioral contrast, which holds that behavioral contrast is the result of the introduction of a less-preferred condition in one component of a multiple schedule.
Journal of the experimental analysis of behavior, 1972 · doi:10.1901/jeab.1972.17-59