Abstract
Time and energy are limited, so animals must be efficient about allocating effort. Motivation to work is positively correlated with reward magnitude. In nature, however, the ease of gaining resources can vary slowly. Animals may therefore need to expend the most effort when rewards are smallest. To study this, we maintained rats in an environment where work was required to earn water. We varied the reward magnitude in long blocks and measured voluntary effort and water consumption. The rats did more trials per day when the reward per trial was smaller, yet consumed more water per day when rewards were larger. We propose an analytic model based on utility maximization which can account for these behavioral observations. The model is based on per-day trial rates, but further explains the timing of trials and suggests a candidate neural substrate. The model spans descriptive, quantitative, normative, algorithmic and mechanistic levels of explanation and makes testable quantitative predictions.
Competing Interest Statement
The authors have declared no competing interest.
Footnotes
preinagel{at}ucsd.edu