Ideomotor Action
Involuntary movement is not always "sensorimotor", which means directly aroused by a sensory stimulus; oftener [{528}] it is "ideomotor", or directly aroused by an idea or thought. It may be so aroused and still be involuntary. We think of a certain result and our muscles produce this result, though we did not really mean to do this act ourselves. The thought arouses the movement because it has previously been linked with the movement. A thought which has previously served as the stimulus to an act will tend to have this effect again, unless inhibited by some contrary stimulus. There is no need of a definite consent to the act, provided there is nothing present to inhibit it.
Good examples of ideomotor action can be observed among the audience at an athletic contest. You are watching one of your team do the pole vault, for instance, and are so much absorbed in his performance and so desirous for him to succeed that you identify yourself with him to a degree. He is rising to clear the high bar, and the thought of his clearing it, monopolizing your mind and leaving no room for the inhibitory thought that the performer is down there in the field and you up here in the stand, causes you to make an incipient leg movement as if you yourself were vaulting.
Voluntary action, in the fullest sense, occurs when you realize the situation and are definitely conscious of yourself, that is to say, when you differentiate yourself clearly out of the total situation, and not only imagine some change to be made, but think of that change as to be produced by you, without at the same time having any contrary thought to inhibit actual execution.