Behavioral variability has been studied mainly by using positive reinforcement. The negative reinforcement of behavioral variability has been analyzed in only two studies (Cassado, 2009; Samelo, 2008) in which escape procedures were used. Based on these studies, the purpose of the present experiments is to investigate behavioral variability under negative reinforcement by using an avoidance procedure and rats as subjects. In Experiment 1 a discrete-trial avoidance procedure will be in effect. Sequences of three lever presses, distributed across two levers, will avoid shocks in each trial and start an intertrial interval in which shocks will not occur. In Phase 1, response-sequence variability will be reinforced according to a reinforcement threshold (RT) procedure. In Phases 2 and 3, avoiding shocks will be independent of variability (Yoked) and dependent on response-sequence repetitions, respectively. Phases 4 and 5 will be replications of Phases 1 and 2, respectively. In Experiment 2, the stimulus control of behavioral variability will be investigated by using the discrete-trial avoidance procedure in effect in Experiment 1. In Phase 1, rats will be exposed to a two-component multiple schedule of reinforcement. In one component, variability will be reinforced and, in the other, avoiding shocks will be independent of variability (Yoked). In Phase 2, the schedule will be similar to that of Phase 1, but the stimuli correlated with each component will be equal (i.e., a mixed schedule of reinforcement). Phase 3 will be a replication of Phase 1 and, in Phase 4, the stimuli correlated wit each component of the multiple schedule in Phase 3 will be reversed. The latency and frequency of response sequences, the proportion of shocks avoided and the U-value will be analyzed in each experiment. The results of the present study will extend those obtained by Cassado (2009) and Samelo (2008) and will allow the assessment of the generality of operant control of behavioral variability to contexts in which avoidance contingencies are in effect.
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