The role of negative instances in the acquisition of the mathematical concepts of commutativity and associativity of a binary operation was examined. Two levels of instruction (positive instances, and positive and negative instances) for commutativity and for associativity were crossed to form a 2 x 2 factorial design with 16 ninth grade subjects per cell. Criterion variables were number of correct responses, stimulus interval, and postfeedback interval during treatments and/or posttests. The results appeared to favor the treatments containing both positive and negative instances and supported the hypotheses that the effect of negative instances transferred from one concept to another. (Author/DT)