An increase in accuracy prior to rule acquisition in a rule based category learning task of six dimensional binary valued stimuli has been consistently observed. To probe whether this increase was a consequence of procedural learning mediated by the striatum, stimuli were divided in to three frequency groups such that subjects responded to some stimuli much more frequently than others. The lack of significant differences in accuracy increases prior to rule acquisition for stimuli with higher numbers of presentations suggests that the relative frequency of stimulus presentation is not relevant to this effect and therefore it is unlikely that this increase is a consequence of procedural learning mediated through the basal ganglia. Subjects demonstrate the same accuracy increase regardless of the number of repetitions of an individual stimulus, and a clear explanation for this effect has yet to come to light. Further possibilities will be explored through future experiments.