A STUDY TO DETERMINE THE RELATIVE EFFECTS OF INCREASING THE NUMBER OF IRRELEVANT STIMULUS DIMENSIONS UNDER SEVERAL DIFFERENT CONCEPTUAL RULES AND INSTRUCTIONAL CONDITIONS. THE RESULTS INDICATED THAT THE EFFECT OF ADDING IRRELEVANT STIMULUS INFORMATION WITH NONCONJUNCTIVE RULES IS SIMILAR TO THAT PREVIOUSLY FOUND WITH CONJUNCTION, A LINEAR DECREMENT IN PERFORMANCE. HOWEVER, THE RATE OF DECREMENT IS GREATER AS RULE DIFFICULTY INCREASES. SIMILAR RESULTS WERE OBTAINED IN A COMPARISON OF INSTRUCTIONAL CONDITIONS. THE LINEAR DECREMENT WITH INCREASES IN IRRELEVANT STIMULUS INFORMATION THUS APPEARS TO BE QUITE GENERAL IN CONCEPT LEARNING, ALTHOUGH THE RATE OF DECREMENT IS HIGHLY DEPENDENT ON SPECIFIC CHARACTERISTICS OF THE CONCEPTUAL PROBLEM. (PsycINFO Database Record (c) 2006 APA, all rights reserved)