What should be measured in psychology? The issue of individual differences

Abstract

I examine the historical origin of the study of individual differences in biology and psychology. A distinction is made between individuation and asymmetryin competencies. Individuation should be analyzed as within-individual consistencies (styles) whereas asymmetry in competencies should be analyzed in terms of the interaction of outcomes of behavioral ontogeny and have no causal properties. These concepts correspond to dispositional categories relevant to different circumstances. Indiviaul differences are important to psychology only form the perspective of the effects of general processes on behavioral ontogeny and individuation.