Abstract:
This study examined the applicability of economic concepts and Allison's (1993) conservation model to wheel-running reinforcement. In preliminary training four female Norway hooded rats learnt to lever press on a fixed ratio schedule for access to a running wheel. In Experiment 1 the schedule was increased then decreased between fixed ratios of one to forty in steps of one per session. Experiment 2 replicated the procedure of Experiment 1 but the ratio was increased in steps of two and the series was repeated twice. Experiment 3 compared a baseline level of performance of rats responding on a fixed ratio of five for wheel-running reinforcement to a condition in which access to wheel-running reinforcement was restricted to every second day only. Experiment 4 used the same procedure as in Experiment 2 except that the reinforcer was condensed milk.
Data in Experiments 1 and 2 revealed unstable k values which made Allison's model inapplicable. The data from Experiments 2 and 4 was analyzed using an equation suggested by Hursh, Raslear, Shurtleff, Bauman, and Simmons (1988) to define demand for wheel-running reinforcement. The experiments demonstrated that demand for wheel-running reinforcement was variable and low. When wheel-running reinforcement was compared to condensed milk reinforcement it was found that rats demonstrated a higher demand for condensed milk. Overall the present series of experiments demonstrate that demand for wheel running is low and extremely variable, thus supporting the conclusion that it may be best characterized as a luxury good that fails to support stable and reliable levels of responding.
