Effect of crowded rearing on negative incentive contrast effect

Female Sprague-Dawley rats were reared under crowded (12 animals per cage) or uncrowded (2 animals per cage) conditions beginning at 30 days of age. At 90 days of age, the subjects were trained to traverse a straight runway for a large or a small food reward, after which all subjects were given additional trials with the small reward. During the preshift phase, crowded and uncrowded subjects did not perform differently, but performance was more rapid with the large magnitude of reward. A trend toward a less disruptive reaction to the downshift in reward among the uncrowded than among the crowded subjects was noted. Since the uncrowded subjects also had heavier adrenal glands (and thus presumably a higher chronic level of stress), it was suggested that they had greater tolerance for the stressful reduction in reward