The Axes of Personality Differentiation

If a single thing stands out in the field of personality differentiation, it is the confusion of tongues and lack of universally recognized canons of systematic procedure. By virtue of a rather arbitrary treatment of the problem, we divided personality into the intellectual and the non-intellectual traits. Even more independence was exercised in classing all non-intellectual traits under temperament and then defining the term with reference to differences in the degree or level of reactivity. We should now inquire if our treatment has been in any way adequate. This is a difficult question and one which deserves careful attention. Proper evaluation centers around the matter of the fundamental modes or axes of personality differentiation. Psychologists need particularly to determine which among their array of personality tests and ratings have a "communality" of determination, as well as the number of fundamentally different constellations involved. The questionnaire tests of psychological "traits" do not help much, for verbal expressions can always be manipulated so that enough will correlate with the few expressions which contain the trait term to make it appear that one can "measure the trait." There is a vast difference between the usefulness of such terms as extroversion, aggressiveness, and emotionality and their significance as valid cues for the study of the constitutional factors which go into personality. But with investigations of personality focused upon different levels of phenomena, it is difficult to even guess at the answers to the problem. Every psychologist recognizes the lack of consistency in the construction of tests and rating scales. Some tests operate at the level of impression, opinion, and interpretation of the behavior of others recalled in retrospect; other tests deal with self ratings or with overt expressive movements. All tests suffer from the apparently insurmountable difficulty that the effects of constitutional and environmental influences do not always vary in the same direction. We may argue, however, that in spite of these drawbacks certain tests show greater communality than others. Thus two non-intellectual traits are more likely to be somewhat co-variable in the same individual than are an intellectual and a non-intellectual trait; that is, high intelligence scores might possibly appear about as frequently with excessive reactivity and nervousness as with excessive lethargy, while tendencies to extroversion might be positively correlated with sociability and low irritability. If this were the case, we might represent the axes of personality differentiation in two different planes. If, however, intelligence and the various temperament traits were all interrelated, with degree of communality the differentiating factor, we would need to have our axes of differentiation in the same plane, as in B of the figure. Finally, if certain non-intellectual traits such as extroversion, introversion, and nervousness were independently variable, it would be necessary to construct a schematic figure of as many planes as there are independent dimensions.

Little assistance in determining the appropriate figure can be derived from the intercorrelations of available personality tests. The author's reason for preferring figure A is based, therefore, upon a physiological argument which later work may show to be inadequate. We have seen reason to believe that the basis of intellectual differences lies in the inherent character of the neuromuscular mechanism, especially in the structuro-functional peculiarities of the higher adjustor centers of the brain. All aspects of response which are directly related to the character of this mechanism should have some communality. But what of the quality and quantity of metabolic energy which runs this machine? Just as we are accustomed to measure the performance of automobiles in terms of the kind of engine operating and the kind of gasoline utilized, so it may be equally legitimate to distinguish between the type of nervous mechanism operating and the quantity and quality of energy-transformation involved. The energy of neuromuscular action is, of course, self contained; but we must not forget that the hormones play an important rôle in the regulation of metabolism. These humoral mechanisms are not of the same order as neural mechanisms and if the two vary independently in individuals, they must be represented in different planes. This analysis is strengthened by the apparent relation of many basic temperament traits with endocrine function. Thus an individual with a high quality neuromuscular mechanism and poor humoral equilibrium and control would be represented near one apex of our double cone, while an individual with high intelligence and good control would be represented near the other apex. Anything further which might be said of this theoretical construction would not assist in the much more important task of unravelling the true axes of personality differentiation. Possibly we may even find as a result of such study that personality is not in any real sense made up of discrete functional units and that the task of seeking multiple axes of differentiation is a scientific "will-of-the-wisp."