PRELIMINARY DATA SUGGESTED THAT MODERATE INHIBITION OF BRAIN ACETYLCHOLINE BY ATROPINE SULFATE MAY HAVE DIFFERENTIAL EFFECTS DEPENDENT ON EITHER NUMBER OF CUES OR MODE OF CUE PRESENTATION. IN A 2 * 2 * 2 FACTORIAL DESIGN WITH RATS AS SS, THE NUMBER OF CUES * DRUG INTERACTION WAS SIGNIFICANT, THUS INDICATING A DIFFERENTIAL RETARDING EFFECT ON LEARNING AS A FUNCTION OF REDUNDANT CUES. CONTROL EXPERIMENTS RULED OUT POSSIBLE DIFFICULTIES DUE TO THE SINGLE CUE CHOICE IN THE MAIN EXPERIMENT. ADDITIONAL EXPERIMENTS FOUND ATROPINE TO HAVE A RETARDING EFFECT ON ACQUISITION OF A SINGLE CUE DISCRIMINATION IN THE PRESENCE OF IRRELEVANT CUES. (PsycINFO Database Record (c) 2006 APA, all rights reserved)