Reactivity and Temperament

Throughout our study of temperament the problem of reactivity has bulked very large. We have mentioned the prevalence of excitability, hypertension and excessive reaction in certain structural types. We have discussed the various physiological processes which mark off the irritable individual from the phlegmatic. We have examined two great classes of insanity, the manic-depressive and the schizophrenic for cues to the level and type of reactivity involved. The net result has been somewhat confusing. On the psychological side we have numerous terms descriptive of special aspects of emotionality; on the physiological side we have structural and functional variations which seem to possess no consistent relation with psychological traits.

At the expense of being wrong, let us try for a more systematic orientation to the problem. Assuming that individuals are graded as to the potential excitatory or inhibitory hormones which can be derived from their endocrine glands, the "normal" hormone-balance and its changes under "emergency adjustments" would make for graded variation in neuromuscular reactivity. Neuromuscular mechanisms have the potentialities of superabundant energy transformation and are constantly tending to overactivity. The normal reactivity level is therefore determined largely by inhibitory hormones, and if these vary in quantity and quality between individuals, response must also vary. Thus the "nervous" child would tend towards overactivity, irritability and instability, because of a lack of appropriate inhibitory hormones, while the "placid," unemotional child would tend to have an excess of these inhibitory substances. But the relation, if existent, is much more complex than this. Persons of phlegmatic temperament often react excessively in emotional crises, whereas persons who exhibit many symptoms of nervousness and hypertension remain outwardly calm and cool.

We need not be entirely confused by this apparent contradiction if we recall that neuromuscular action is held in check by neural inhibition as well as by hormonal inhibition. An individual with a deficiency of hormonal inhibition must compensate by establishing greater neural inhibition if he is successfully to coordinate his activities; when an unexpected situation arises, he is therefore more able to maintain his balance than is a predominantly hormonal controlled individual. It may be significant in this connection that, following crises, persons who have had their excess activity under some degree of "voluntary" neural inhibition gravitate toward schizophrenia whereas more phlegmatic persons gravitate towards manic-depressive stupor. One might postulate that the typical manic-depressive represents excessive unchecked hormonal excitation and inhibition, while the typical schizophrenic represents deficient hormonal inhibition, fortified with an acquired excess of neural inhibition; but these speculations lead us again into all the fallacies of type thinking which we should steadfastly avoid. A further factor in this inconceivably complex problem is the rôle which environmental demands have placed upon individuals differing in their potential level of reactivity. Presumptively, a naturally nervous child may have his nervousness either enhanced or brought under control as the result of living in a difficult and trying situation.