Simultaneous incentive contrast effects with alcoholic and nonalcoholic beverages as the discriminanda for reward magnitude

Abstract

Alcoholic and nonalcoholic beverages consumed by rats prior to runway conditioning trials served as cues for reward magnitude. Learning under the alcoholic (but not the nonalcoholic) cue condition appeared to be state dependent. Under both conditions, a simple effect for reward magnitude occurred, but positive and negative incentive contrast effects occurred under only the alcoholic condition. The symmetrical contrast effects seem consistent with the view that alcohol enhances positive states rather than reduces negative ones.The simultaneous incentive contrast paradigm involves training subjects to respond in the presence of two different stimulus cues, each of which is associated with a different value of a reward parameter. If, in the presence of the cue associated with the less valuable reward, subjects perform at a lower level than control subjects receiving only the less valuable reward, a negative incentive contrast effect is said to occur. Similarly, if, in the presence of the cue associated with the more valuable reward, subjects exceed the performance of control subjects receiving only the more valuable reward, a positive incentive contrast effect is said to occur. Negative contrast regularly occurs in simultaneous studies, while positive contrast generally fails to appear (see Cox, 1975).A variety of discriminative cues have been employed in studies of simultaneous incentive contrast effects. With animal subjects, however, the cues most typically have been a black and a white runway. Characteristically, experimental animals receive a small food reward in one runway and a large food reward in the other runway; trials are administered in an intermixed fashion between the two runways; and speed of running in each runway is the measure of performance.The present experiment also involved within-subjects runway conditioning for two magnitudes of a food reward, but the animals were always run in the same gray runway. For the experimental animals, the discriminative cues for the two reward magnitudes were alcoholic and nonalcoholic beverages consumed immediately before the conditioning trials. Prior research has indicated that centrally acting drugs readily serve as discriminanda in differential conditioningRequests for reprints should be sent to W.

A motivational model of alcohol use.

“…To explore these possibilities, Cox and colleagues (Cox, 1981(Cox, , 1988Cox, Klinger, & Kemble, 1987) compared reactions to incentive shifts of rats that had consumed an alcoholic solution prior to their conditioning trials with those that had consumed a nonalcoholic solution. Results obtained with the sober rats were consistent with those of the many incentive contrast studies that have followed those of Crespi (1942) and Zeaman (1949).…”

“…That is, alcohol, through its attenuation of the negative emotional reaction to a downshift in reward, might reduce or eliminate the negative incentive contrast effect. Through its enhancement of a positive emotional reaction to an upshift in reward, alcohol might contribute to a positive incentive contrast effect.To explore these possibilities, Cox and colleagues (Cox, 1981(Cox, , 1988Cox, Klinger, & Kemble, 1987) compared reactions to incentive shifts of rats that had consumed an alcoholic solution prior to their conditioning trials with those that had consumed a nonalcoholic solution. Results obtained with the sober rats were consistent with those of the many incentive contrast studies that have followed those of Crespi (1942) and Zeaman (1949).…”

The effect of ethanol on activity level following reward shift

“…Thus, alcohol not only counteracted the depressed reaction to the incentive reduction ; it led to an opposite reaction-invigoration. Alcohol has previously been observed to alter vastly animals' reactions to incentive shifts (Cox, 1981). This alteration may account for organisms ' motivation for using alcohol when they exper ience incentive losses.…”

Effects of alcohol on successive incentive contrast

“…From the viewpoint that alcohol reduces negative emotional states (West & Sutker , in pres s), alcohol would be expected to counteract the negative emotional reaction to downshifts in reward and thus reduce or eliminate entirely the negative -incentive contrast effect. From the viewpoint that alcohol enhances positive emotional states (Cox , 1981), alcohol would be expected to contribute to rats' elation following upshift s in reward and thereby foster the development of a positive-incentive contrast effect. I…”