In Strelau’s theory of temperament (RTT), there are four types of temperament, differentiated according to low vs. high stimulation processing capacity and to the level of their internal harmonization. The type of temperament is considered harmonized when the constellation of all temperamental traits is internally matched to the need for stimulation, which is related to effectiveness of stimulation processing. In nonharmonized temperamental structure, an internal mismatch is observed which is linked to ineffectiveness of stimulation processing. The three studies presented here investigated the relationship between temperamental structures and the strategies of categorization. Results revealed that subjects with harmonized structures efficiently control the level of stimulation stemming from the cognitive activity, independent of the affective value of situation. The pattern of results attained for subjects with nonharmonized structures was more ambiguous: They were as good as subjects with harmonized structures at adjusting the way of information processing to their stimulation processing capacities, but they also proved to be more responsive to the affective character of stimulation (positive or negative mood).