Complex Effects of Reward Upshift on Consummatory Behavior in Rats

ANNICCHIARICO, I. ; GLUECK, A. ; CUENYA, L. ; KAWASAKI, K. ; PAPINI, M. R.

Bogota

Congreso; 17th Biennial Meeting of the International Society for Comparative Psychology; 2014

International Society of Comparative Psychology

Exposing rats to an upshift from a small reward to a larger reward sometimes yields evidence of successive positive contrast (SPC), an effect that could be a suitable animal model to study positive emotions. However, SPC is notable for its unreliable occurrence. A series of experiments explored the effects of reward upshift under several conditions in terms of consummatory behavior. Several experiments with various sucrose concentrations produced occasional evidence of SPC, but mostly a significant impairment of behavior relative to unshifted controls always exposed to the large reward. These results are consistent with competition between processes causing opposite changes on behavior. On the one hand, reward upshift causes an increase in behavior dependent on the absolute or perhaps relative reward value; on the other, the upshift may induce processes that suppress behavior, such as taste neophobia (induced by an intense sucrose taste) and generalization decrement (induced by novelty in stimulus conditions after the upshift). A final experiment tested the role of neophobia and generalization decrement by preexposing animals to either the upshift concentration (12% sucrose) or water during three days before the start of the experiment. Animals preexposed to sucrose drank significantly more that the animals preexposed to water and just as much as unshifted controls, although no evidence of SPC was observed. Thus, reward preexposure reduced either neophobia or novelty to eliminate the suppression induced by the reward upshift, but it did not induce SPC.