The study examined the effect of dyadic interaction on the use of implicit knowledge in a perceptual categorization task. In the first phase, participants memorized images of the target category. In the second and the third phases they categorized new stimuli. In the dyadic condition the second phase was held in a pair, and the third phase individually. In the individual condition participants completed all three phases on their own. Implicit knowledge was observed in both groups, but its stability was higher after work in pairs. Awareness of the implicit rule in both conditions was low, however participants of the dyadic condition mentioned less irrelevant characteristics of stimuli in the postexperimental questionnaire. The results indicate that dyadic interaction promotes the use of implicit knowledge. Refs 23. Figs 1. Tables 3.