and colors. Either color or form was made relevant by holding constant the other dimension; so, for instance, a form problem might be: red square vs red triangle, and a color problem: green diamond vs yellow diamond. Within the first six problems of a daily session, there was no repetition of color or form cues. The relevant cues on the critical seventh trial were also novel for that day. On repeated sessions for the same S, the specific cues were re-paired randomly from a population of 18 form and 12 color cues. In Experiment 2, the population consisted of 12 forms and 12 colors.