Negative incentive contrast effects with sucrose and rats as due to aggression

Abstract

Three equal groups (n=20 each) of rats received 10 sessions of barpress training for 16% or 4% sucrose solutions or tap water. On Session 11, the 16% group was changed to a 4% (constant volume) sucrose solution. Negative contrast occurred. Moreover, on the postshift days, the number of times the downshifted subjects bit a bottle brush was statistically greater than the control group, indicating greater aggression in the shifted than in the nonshifted animals. Furthermore, the shifted subjects displayed no frustration effect in the double runway. These data, together with one other study in the literature, speak to an aggression account of the downward contrast effect rather than a frustrative account of the negative phenomenon. Future research should provide further validity information on the two dependent measures used herein.