The effects of reward quality on risk-sensitivity in Rattus norvegicus

Risk-sensitive foraging theory (RSFT) was developed to explain a choice between a variable (risk-prone) or constant (risk-averse) option. In the RSFT literature, qualitative shifts in risk-sensitivity have been explained by fluctuations in daily caloric energy budget (DEB). The DEB rule describes foragers' choices as being based on fitness and rate of gain. If the DEB rule is correct, rewards that differ in caloric returns should cause differences in foragers' sensitivity to risk. However, few studies have explored the influence of reward quality on risk-sensitivity in mammals. The present study was designed to examine the effects of reward quality on risk-sensitivity when reward magnitude, delay to reward, body mass, and response effort were controlled. Results from the current study demonstrated that subjects rewarded with a high calorie reward (i.e., sugar) made significantly fewer choices for a variable option than subjects rewarded with a lower calorie reward (i.e., grain). These results are consistent with the predictions of the DEB rule, and add to the RSFT literature where reward quality was manipulated by describing difference in risk-sensitivity in mammals. Suggestions for future research include an examination of risk-sensitivity where flavor and caloric return are manipulated.