This study explored the methodological implications of a source of experimental contamination, the goal events and, presumably, consequent odors of preceding animals. Rats received reward (R) and nonreward (N) in double-alternation sequences, with the experimental treatments resulting from variation in the particular sequences administered to members of a squad. The results suggested that differential odors exuded by preceding Ss on R and N trials can serve as discriminative cues signalling R or N, but that the odor cue from the immediately preceding trial could be neutralized by prior odors of the other kind. Constancy of schedule enhanced the discrimination. © 1969, Psychonomic Journals, Inc.. All rights reserved.
