Conditioned reinforcement dynamics in three-link chained schedules.
Unique stimuli in each chain link build stronger conditioned reinforcers than food proximity alone.
01Research in Context
What this study did
The team built a three-link chain. Each link ended with a brief light or tone. Food arrived only after the final link.
They asked: do the middle stimuli work like mini-rewards because they are close to food, or because they point to the next stimulus?
What they found
Both things mattered. A stimulus gained power from being near food and from announcing the next link.
When each link had its own unique look, the chain held together better. Sameness weakened control.
How this fits with other research
KELLEHEBERRYMAELLIOTT et al. (1962) already said chained schedules can create new reinforcers. Cooper (1997) shows exactly how: differentiate the cues.
Rosenblith (1970) saw rats drink when a light promised food. Cooper (1997) adds that unique cues sharpen this promise along the whole chain.
Duker et al. (1996) found visual beats auditory for keeping behavior steady. Cooper (1997) agrees: make each visual link distinct and control grows.
Why it matters
When you run token boards or response chains, give each step its own clear picture or sound. The token right before candy will stay powerful, but the earlier tokens also need unique looks so they don’t blur together. Better discrimination now means stronger conditioned reinforcement later.
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02At a glance
03Original abstract
In two experiments rats were trained on three-link concurrent-chains schedules of reinforcement. In Experiment 1, additional entries to one terminal link were added during one of the middle links to a baseline schedule that was otherwise equal for the two chains, and, depending on the condition, these additional terminal-link presentations ended either in food or in no food. When food occurred, preference was always in favor of the chain with the additional terminal-link presentations (which also entailed a higher rate of reinforcement). When no food occurred at the end of the additional terminal links, the outcome depended on the nature of the stimuli associated with these additional terminal links. When stimuli different from the reinforced baseline terminal links were used for the no-food terminal links, preference was against the choice alternative that led to the extra periods of extinction. When the same stimulus was used for the two kinds of terminal links, preference was near indifference, that is, significantly greater than when different stimuli were used. In Experiment 2, rats learned repeated reversals of a simultaneous discrimination under a three-link concurrent-chains schedule, in which the food or no-food choice outcomes were delayed until the end of the chain. Different conditions were defined by the point in the chain at which differential stimuli occurred. When the middle and terminal links provided no differential stimuli, discrimination was acquired more slowly than when differential stimuli occurred in both links. When differential stimuli occurred in the middle but not the terminal links, acquisition rates were intermediate. Both experiments together show that the effects of stimuli in a chain schedule are due partly to the time to food correlated with the stimuli and partly to the time to the next conditioned reinforcer in the sequence.
Journal of the experimental analysis of behavior, 1997 · doi:10.1901/jeab.1997.67-145