The science of life : fully illustrated in tone and line and including many diagrams

BOOK 8

would seem to be a difference in ease of dissociation. ‘The extrovert is able to keep conflicting ideas apart—to use a popular phrase, in ‘‘ watertight compartments ’’—and thus to assimilate cheerfully and with equanimity the most divergent experiences. In the introvert, on the other hand, the mind is more unified ; its different parts cannot be kept apart, but are continually infringing on each other; and much of his mental life is occupied by their attempt to fit themselves together into logical, harmonious schemes. ‘The more discordant elements are fiercely repressed and may become troublesome complexes, while in the extrovert they are simply walled off from the rest of the mind.

Recently, McDougall has hit on an ingenious method which throws some light on the constitutional differences between extrovert and introvert. The accompany-

ing figure represents a cube; but as

you look at it, it shifts its perspective—now one of its two square faces is nearer you, now the other, now it is sloping up and to the right, now down and to the left. Ifyou look fixedly at the figure without trying to force on it either of the two possible perspective interpretations, you will find that it changes from one to the other at more or less regular intervals. McDougall found that the interval varied very much for different people ; and that it was much longer for extroverts, much shorter for introverts. Here evidently we have a model on a small scale of the way in which the mind reacts to the graver conflicts of life. ‘The two interpretations of the figure are mutually exclusive, and equally satisfactory. When one of them is adopted, the other must be inhibited. In the extrovert, such an arrangement is comparatively stable ; in the introvert the inhibitory process is feebler and the two rival interpretations are continually struggling for supremacy.

But the most interesting thing that emerged from this investigation was that the rate of alternation could be altered in one and the same individual by the use of drugs. Quite small amounts of ether or

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The Deceptive Cube.

Fig. 327.

THE SCIENCE OF LIFE

CHAPTER 7

alcohol would lengthen the interval to double or quadruple, while coffee or strychnine would speed up the change. “The drugs of the two classes were perfect antagonists ; for example, during the hastening produced by strychnine, which lasted several hours, a whiff of ether or a dose of alcohol temporarily antagonized and reversed its effect.”

It is perhaps unfortunate that these terms extrovert and introvert have come to be so widely used, for they give a false impression of simplicity, as if the world was really just two sorts of human beings, “ extroverts’’ and ‘“‘introverts,” as distinct as males and females. It would be truer to say that everyone fluctuates between extroversion and introversion. Some of us have a bias one way and some another, but a glass of wine may make us more extrovert and a cup of coffee swing us towards introversion. Recently new suggestions have come from another quarter. Our knowledge of heredity, of physiology, of brain-structure and brainfunction has forced upon us the view that body and mind are not distinct entities, but two expressions of the unitary living organism. In actuality, they are inextricably entangled. On this view, minds and bodies (for we cannot help continuing to make the distinction between them for convenience sake) would not be expected to stand in a haphazard relation with each other, any kind of mind with any kind of body, but certain types of mind and body should go together. We have already maintained this view for male and female instincts (Book 4, Chap. 6, § 8); we have refused to believe that a fully masculine soul could inhabit a fully feminine body, or vice versa. Now we are extending this idea to cover the various temperaments. We are asserting, contrary to such pre-scientific notions as reincarnation, or the idea that a waiting soul somehow slips into a body when the body has reached a certain stage of development, that soul and body are both aspects of one whole, the mind-body, the living human being, who is always different from every other individual human being.

Kretschmer, in his book Physique and Character, gives some account of recent work in this field. In his psychiatric practice he noticed that certain kinds of insanity went together with certain kinds of body-build. Those who suffered from the manic-depressive type of madness were usually stout and stocky, big-waisted, well-covered, with rather barrel-shaped bodies, short neck