Complex effects of reward upshift on consummatory behavior

• Published in: Behavioural processes Vol. 129; pp. 54 - 67
• Main Authors: Annicchiarico, Ivan, Glueck, Amanda C., Cuenya, Lucas, Kawasaki, Katsuyoshi, Conrad, Shannon E., Papini, Mauricio R.
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 01.08.2016
• Subjects: Animals; Conditioning, Operant - drug effects; Consummatory Behavior - drug effects; Consummatory successive positive contrast; Dose-Response Relationship, Drug; Female; Generalization decrement; Incentive relativity; Male; Neophobia; Rats; Reward; Saccharin - pharmacology; Sucrose - pharmacology; Neophobia; Incentive relativity; Generalization decrement; Consummatory successive positive contrast
• ISSN: 0376-6357; 1872-8308
• DOI: 10.1016/j.beproc.2016.06.006

•No extensive research on successive positive contrast (SPC) has been published.•A series of 10 experiment report transient consummatory suppression.•However, no evidence of consummatory SPC was found.•The status of SPC as a phenomenon is called into question. Exposing rats to an upshift from a small reward to a larger reward sometimes yields evidence of consummatory successive positive contrast (cSPC), an effect that could be a suitable animal model of positive emotion. However, cSPC is an unreliable effect. Ten experiments explored the effects of an upshift in sucrose or saccharin concentration on consummatory behavior under several conditions. There was occasional evidence of cSPC, but mostly a combination of increased consummatory behavior relative to preshift reward concentrations and a reduced behavioral level relative to unshifted controls. Such a pattern is consistent with processes causing opposite changes on behavior. Reward upshift may induce processes that suppress behavior, such as taste neophobia (induced by an intense sucrose taste) and generalization decrement (induced by novelty in reward conditions after the upshift). An experiment tested the role of such novelty-related effects by preexposing animals to either the upshift concentration (12% sucrose) or water during three days before the start of the experiment. Sucrose-preexposed animals drank significantly more than water-preexposed animals during the upshift, but just as much as unshifted controls (i.e., no evidence of cSPC). These results suggest that cSPC may be difficult to obtain reliably because reward upshift induces opposing processes. However, they also seriously question the ontological status of cSPC.