psychology is, "to determine the simple reaction-time, and from it to find the factors of psycho-physical time—namely, perception-time, apperception-time (or discernment-time), and will-time."[1]
Along this line laboratory investigation has been able to show that the will does, as a matter of record, occasion changes in the central physiological mechanism, and that these changes possess quantitative differences having more or less definite relation to psychical activity. By this I understand that the latent energy of the nerve-cells is summoned to activity, and that, as a result, the brain labors hard. In our own laboratory I have seen the subject of an attention experiment pour with perspiration, although physically he was, to all appearance, quite quiescent. No better proof of intense cerebral work could be desired. And experiment simply attempts to relate this energizing to the concomitant psychological states.
But Wundt has committed himself to the modern attitude even further. In the first and second editions of his "Physiological Psychology," he suggested that the frontal regions of the brain are related to apperception as the "bearers of the physiological processes which accompany the apperception of the presentations of sense."[2] In other words, all stages of the apperceptive process are accompanied by a fixed physiological activity. Beyond the circumstance that this assigns a function to the frontal regions which, otherwise, stand out of distinct relation to the factors of consciousness, it must be regarded as a speculation. Wundt himself, although he does not dismiss the hypothesis, tends to minimize it from his third edition. Yet it serves to show how persistently he clings to the true psycho-physiological method even in regard to the most recondite operation of the mind.
It remains to note that the influence of mind over body demands study as much as the converse. If apperception be a legitimate supposition—and it would seem to be a hypothesis which at least accounts for unquestioned facts, then it follows that we must estimate it, not by external stimulus, but in terms of internal activity. And this, of course, reminds us that psycho-physiological investigation has proved the existence of an influential voluntaristic element. No doubt, to this point, the former has claimed, and still claims, the lion's share of experimental attention. So that, in many ways, the internal problem awaits concentrated attack. That is to say, physical and physiological problems, being so much more readily amenable to the new methods, have tended to crowd out the distinctively psychological material. Nevertheless, we have arrived at something analogous to a causal influence of the central nervous system upon what I shall call ideation. This was the indispensable initial step. But yet, this causality is
