Habit Formation in Rats Trained on a Fixed-Ratio Schedule of Reinforcement (2012)

Undergraduate: Ian Everitt

Faculty Advisor: Donita Robinson
Department: Biology

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Different schedules of reinforcement generate different behavioral patterns in rats trained to perform operant behavior tasks. Goal-directed behavior is traditionally defined as behavior sensitive to changes in reward value and action-outcome contingency (the relationship between behavior and reward). In contrast, habitual behaviors are inflexible and less sensitive to changes in reward value and action-outcome contingency. A ratio schedule of reinforcement that supplies a reward based on the amount of an operant behavior typically generates goal-directed behavior but can lead to habitual behavior after extended training. In this study, the transition from goal-directed to habitual behavior was compared in rats trained to self-administer solutions of 1.5% or 10% sucrose. After 4 weeks of fixed-ratio operant training, habitual responding was evaluated by 3 satiety-specific devaluation tests conducted over 6 weeks. Finally, habitual behavior was assessed before and after contingency degradation training that dissociated the action-outcome contingency. Results suggest that rats trained to self-administer 10% sucrose demonstrate goal-directed behavior, while rats trained to self-administer 1.5% sucrose display conflicting results that may indicate an underlying appetizer effect. Groups of 10mM MSG and 10% ethanol were added to compare additional reinforcers. These data reveal differences in outcomes of standard tests of goal-directed behavior depending on the specific reinforcer.