Wheel-running in discrete trial and operant paradigms under various effort requirements

Two experiments were conducted in which the wheel-running behavior of rats under various effort requirements was investigated. The specific effort requirements were obtained by varying the tangential force required to initiate wheel movement. In the first experiment, a discrete trial preparation was used in which 4 groups of rats received training with high effort levels of 90, 110, 130, and 150 g. The results showed that increasing effort requirements slowed the rate of acquisition, lowered the asymptotic running speeds, and reduced resistance to extinction. In the second experiment, using an operant preparation, running speeds were examined for baseline (nonreinforced) and fixed-interval 1 min schedules of reinforcement at effort levels of 45, 90, and 180 g. The results clearly showed wheel-running to be schedule-induced. However, the effects of effort on FI behavior were less clear due to inconsistencies between subjects. Results are discussed in terms of the potential benefits of bridging operant and discrete trial preparations and methods for studying the effects of effort on animal behavior.