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Document Type

Article

Abstract

Previous results have demonstrated that rats' rates of lever pressing for 1% liquid sucrose increase if a period of food-pellet reinforcement will soon occur (i.e., positive induction). The present study investigated whether this induction would be altered by changes to the amount of time the reinforcers were available and/or by their temporal relation to one another. In Experiment 1, subjects responded in 50-min sessions in which 1% sucrose reinforcement was delivered in the initial portion of the session and food pellets were delivered in the final portion. The lengths of these portions varied across conditions. Similar induction effects were observed across conditions. In Experiment 2, subjects responded for sucrose reinforcement in the initial portion of the session followed 25 min of food-pellet reinforcement. The length of the initial portion varied across conditions. Similar induction effects were again observed across conditions. In Experiment 3, subjects responded on a multiple schedule in which 1% sucrose was always delivered in the first component and food pellets were always delivered in the second. Component duration was varied across conditions. Results showed that response rates for sucrose varied inversely with component duration, but these results may have been due to poor discrimination between components at short component durations. Thus, Experiment 4 replicated the procedure of Experiment 3 except, in the second component, the lever was removed from the chamber and food pellets were delivered independently of responding. Response rates for sucrose did not vary with component duration in this procedure. The present results indicate that the present induction effect is relatively robust against changes in component variables. They also suggest that the effect is fairly general, with the controlling factors likely occurring at a molar level.

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