The energies of men : a study of the fundamentals of dynamic psychology / by William McDougall.

  • McDougall, William, 1871-1938
Date:
1933
Catalogue details

Licence: In copyright

Credit: The energies of men : a study of the fundamentals of dynamic psychology / by William McDougall. Source: Wellcome Collection.

    69/434 (page 45)
    The Reflex Theory of Instinct Many authors have assumed that every instinctive activity can be explained in terms of some fixed system of connexions between sensory and motor nerves ; that is to say, they have accepted what is known as the mechanical reflex theory of instinctive activity. According to that theory, each particular movement made in the course of an instinctive activity is a response to some particular physical impression or stimulus falling on some sense-organ ; the stimulus, it is supposed, causes the response by way of an explosive tremor which, having been initiated in the sense-organ by the stimulus, runs along a sensory nerve into the central nervous system, there spreads over to a motor nerve and so out and away to a muscle. And it is assumed that the essential innate basis of any instinctive action is an appropriate system of such connexions between sensory and motor nerves—only this and nothing more. Now this account is perhaps true as far as it goes and as long as it does not profess to be a complete account and explanation. The instinctive activity does involve per¬ petual reception of sense-stimuli, and the spreading of con¬ sequent sensory excitations into and through the central nervous system and so out along motor nerves to muscles (to muscles of the viscera, bowels, stomach, heart and arteries, and to various glands, as well as to the so-called voluntary muscles of the head, limbs and trunk). In two respects this reflex-theory of instinctive activity is very inadequate. First, it neglects to notice and does not explain the fact that the wasp’s cell-building actions are guided, not merely by discrete sense-stimuli, but by some appreciation of the cell as a whole. Such appreciation is an activity which we cannot directly observe ; we infer it from the observed fact that the wasp’s movements are adjusted to, and in some sense determined by, the cell as a whole. The cell, begun at the end which is to remain closed, is first expanded and then contracted as it nears completion ; so that its cavity assumes the form of a long oval suited to the 5