Physiological Variations and Temperament

The urge to classify men and their reactions into types was never more apparent than in the diagnosis of temperamental differences. Exceptional development of a personality "trait" in one individual leads to a search for additional cases that will fit the same category and a corresponding neglect of the concept of continuous gradation. Thus the terms "extrovert" and "introvert" do not properly refer to two mutually exclusive categories, into one of which each individual must fit; rather, they are descriptive of the extremes of one aspect of behavior which shows a normal distribution.

In spite of their growing realization of the fallacy of type thinking, psychologists have lately given particular attention to the relation of alleged temperamental peculiarities and various body types. The psychoanatomy of types, as this concept might be called, assumes that men can be pigeonholed into several rough divisions according to their general structural development. It assumes, furthermore, that these divisions will correspond, also roughly, to fundamental differences in temperament. This notion can be traced as far back as Hippocrates. Various individuals, mostly clinicians, have since contributed to it, their main service apparently being the substitution of new terms for old.

Physiological variations are not as obvious as are structural variations; furthermore, they can be measured only indirectly and with elaborate instrumentation. Measurable variations which are probably significant for our problem include metabolic rate, vascular and electrical skin changes, muscular tension, and the acidity of the blood, urine, and saliva. These changes may be interpreted variously as indicating the level of organic reactivity, the relative spread of neural impulses, the rate of oxygen reduction during neuromuscular activity, and the general type of biochemical reaction involved. Differences in the hormone content of the blood undoubtedly are significant also.

For purposes of comparison, the boys were divided into groups of high, medium, and low weight loss, those with high loss having a high metabolic rate and vice versa. The high loss group had a faster pulse rate and seemed to show the most pronounced introvertive tendencies. The low loss group gave test results indicative of extraversion. Data obtained from medical students and a few psychotic patients also confirmed the general conclusion that persons with high metabolic rate tend to be introvertive, intense, and irritable.

It is difficult to say just what all these complicated chemical measures indicate in terms of general organic reactivity or of differential body chemistry, especially since directly contradictory statements appear in most of the reports. In the absence of adequate information it is easy to be led into abortive speculations. Thus one writer foretells the day when biochemists will have proved that "a deficiency of sulphatide phosphorus and a high oxidative reduction-potential on a certain area of the cerebral cortex is invariably associated with the creation of great poetry," and another proposes that "the physician of the future will have bottled hormones labeled 'happiness,' etc." Such seductive verbalism minimizes the tremendous obstacles which are yet to be surmounted. The fields of biochemistry and endocrinology are only beginning to be opened up, and to jump at them as an explanation of all personality differences is futile and unwise. The present trend of evidence is positive, and should be taken to indicate the necessity for study with more refined techniques.