On the Voluntary Control of the Force of Movement

The muscle sense, if the term be used in a comprehensive way to include all sensations arising in the interior of a muscular member of the body, furnishes sensations that form the basis of a variety of perceptions. Judgments of weight and resistance, of extent of movement, of speed and force of movement, and of position, are all based in large measure on this class of sensations. There have been more or less definite attempts to reduce some of these types of perception to others, as for instance to explain the perception of the extent of movement as a derivative from the perception of the time of movement. In another place, I have brought together a variety of evidence all going to show that the extent of a movement is not inferred from judgments of the force and duration of the movement or from a comparison of the initial and terminal positions of the movement. These other judgments may indeed assist in certain cases. But there exists a judgment of extent, independent and in its own right. The present paper is an attempt to examine the force of movement in a similar way. The main question is whether the force of a movement is perceived directly or inferred from a perception of extent. Any form of apparatus in which force is applied gradually to a spring—as in a dynamometer or ergometer—serves admirably to raise this question, but not to answer it. In such an apparatus, increase in the force of movement is only to be attained by increasing the extent; and it does not appear whether the force is perceived directly or in terms of the extent.