Control of reward expectancies by drive stimuli

In 3 experiments with 160 rats, the successive negative-contrast effect (NCE) was eliminated or reduced by changing drive level along with the decrease in reward size. The reduction in the NCE was not due to changing drive per se, but rather to the fact that the drive when small reward was experienced was different from that when large reward was experienced. Thus, the NCE occurred if large- and small-reward trials were given under the same drive, even if large-reward trials under a different drive intervened. Also, following the lack of an NCE under different drive, the NCE occurred when small reward was subsequently received under the same drive as the large reward. Results are interpreted as indicating that drive stimuli have strong control over reward expectancies relative to the control exercised by other stimuli, such as alley stimuli. (PsycINFO Database Record (c) 2006 APA, all rights reserved).