Temporal discounting in RHA/Verh and RLA/Verh rats: Adaptation to food deprivation

The aim of the research was to test the hypothesis formulated by Ostaszewski, Karzel, and Szafranska (2003) that the way the rate of discounting of delayed food rewards changes in response to deprivation procedure depends on the temperamental characteristics of the animals. We performed a systematical replication of our previous studies, with more severe deprivation procedure, and with rats of both genders, coming from two different sublines: RHA/Verh, and RLA/Verh, the former being less emotionally reactive. There were no between strain differences in the discounting. However, we found that the deprivation procedure affected the rate of discounting only in the more reactive strain (RLA/Verh): the rats during deprivation discounted delayed rewards more steeply, then after the deprivation was withdrawn. Moreover, rats of the different genders appeared to systematically differ in the rates of discounting: female discounted the value of delayed food rewards at a higher rate than male rats did. Based on this and other work, we conclude that the apparent similarity of the discounting process across species and genders, as well as similarities of the direction of differences between the genders and environmental richness reported in human and animal studies, support the claim that the discounting process is a general, biological process with highly important adaptive value for all animals.