Incentive preference as a function of mode of training, sucrose concentration, and water deprivation in the rat

Abstract

Highly and moderately water-deprived animals (23.5 hand 18 h, respectively) were exposed to 8% sucrose and water or 20% sucrose and water at fixed positions in a two-choice discrimination apparatus. Half the animals in each group received a series of alternating free-and forced-choice trials. The other animals received a series of forced-choice trials prior to a free-choice preference test. A retesting procedure was carried out in which deprivation levels were switched for all animals. Neither mode of training, exposure to incentive, nor concentration of sucrose reliably affected incentive preference. Deprivation level, however, was related to incentive preference. Only animals that were initially moderately deprived developed reliable and consistent preferences to sucrose. Highly deprived animals also developed reliable sucrose preferences after being switched to moderate water deprivation during retesting.Beck and Bidwell (1974) exposed highly waterdeprived (23.5 h) and nondeprived rats to sucrose (8%) and water at fixed positions for a lengthy series of alternating free-and forced-choice trials. Nondeprived animals developed high sucrose preferences, while the water-<ieprived animals displayed no incentive preferences. These results replicated earlier fmdings for animals not given such prolonged exposure to each incentive (Beck & Nash, 1969; Beck, Nash, Viernstein, & Gordon, 1972; Beck, Self, & Carter, 1965). Cohen and Obstendorp (1976) and Cohen, Obstendorp, and Ross (in press) carried out experiments similar in design to Beck and Bidwell's (1974) but found reliable sucrose preferences in highly and moderately water-deprived animals (22.5 and 18 h). These recent studies differed from Beck and Bidwell's work in that animals were exposed to a higher concentration of sucrose (20%) and received a series of forced-choice trials prior to freechoice tests for preference. The present study was carried out to determine if these differences in mode of training and sucrose concentration could have caused such contradictory findings. METHOD SubjectsNinety-six male albino rats (Wistar strain) from the breeding colonies of Woodlyn Farms, Guelph, Ontario, Canada, approximately 80 days of age at the time of pretraining, were used.