Behavioral heat intake as a function of reward duration in rats

Abstract

Animals working for heat in a cold environment increase responding when reward duration is reduced, but in many instances the increase in responding is not sufficient to prevent a decrease in the amount of heat obtained. Eight experiments were conducted to investigate the reason why rats' barpress responses for heat are less efficient at short reward durations. The results show that a ceiling effect is not involved and also that improper response-topography or differences in whole-body heat absorptivity or in response effort cannot explain the phenomenon. Evidence was found for the hypothesis that response rate does not increase sufficiently at short reward durations because many short rewards produce a greater afferent signal than do few long rewards. This inequality seems to be caused by characteristics of the stimuli that result in a greater relative change in skin temperature (.:1T)or in the rate of change of skin temperature (aT/at) for short-duration rewards.