SCHEDULE OF PARTIAL REWARD AND NEGATIVE CONTRAST EFFECT

Trained 3 groups of rats (13 each) in a runway (3 trials/day for 8 days) under either consistent reward (.09 gm.) or partial reward (.90 gm.) prior to being shifted on Days 9 and 10 (15 and 10 trials, respectively) to .09 gm. consistent reward. 1 partial schedule contained transitions from nonrewarded to rewarded trials (LNL), the 2nd schedule did not (LLN). The negative contrast effect in Group LLN was greatest and appeared sooner in the goal section, diminishing progressively in earlier alley sections. On Day 10, differences between groups disappeared. Data were compared with those of earlier studies which employed random schedules of reward. Results provide additional support to the growing tendency to interpret negative contrast effects in terms of associative variables which are ultimately sequential in origin. (PsycINFO Database Record (c) 2006 APA, all rights reserved). © 1969 American Psychological Association.