Rat Strategies and the Interactive Schedule: A Multidimensional Examination of Behavior

The ways in which the variables time, distance, and force or effort mediate behavior were examined. Rats' running in a running wheel under various schedule conditions was studied by implementing the interactive schedule (Berger, 1988), a schedule in which a continuum of reinforcement contingencies is used. The variables of time and distance were manipulated via four points on the continuum. One point was a pure fixed-interval schedule, one was a pure fixed-ratio schedule, and the remaining two points on the continuum were hybrids of those two schedules. Additionally, the effect of effort on behavior was examined by setting the tangential force requirement on the running wheel to 20 g or 80 g, resulting in eight conditions. The dependent measures were distance per session, reinforcers per session, distance per reinforcer, and move speed. Results indicated that the rats responded in a manner that was neither a pure time-minimization strategy nor a pure distance-minimization strategy, suggesting that rats attend to the dimensions of time and distance simultaneously. Additionally, increased force and effort suppressed the rats' running under all schedule conditions. The importance of studying foraging behavior within a multidimensional model viewpoint is discussed.