PHYSIOLOGICAL PSYCHOLOGY 231
ingly, it must submit to experimental treatment. A process exists, therefore analysis is free to track it to its lair. And, especially when the problem of duration raises its head, as it does inevitably, a cumula- tive series of experiments is in strict order.
What happens when apperception occurs? Generally, of course, a transformation of sensory into motor activity. In detail, according to Wundt, a train of processes has supervened, viz.: (1) Transmission from the sense-organ to the brain; (2) entrance into the "field of view," that is, existence of simple perception; (3) entrance into the "point of view," when perception becomes discernment; (4) activity of will, with innervation of the central organism through the motor- nerves, and (5) the resultant excitation of the muscles. Plainly, the crux hides in (3), which is purely psychological, while the others have a clear physiological reference. Nevertheless, (3) happens to be so surrounded by physiological phenomena that it is open to observation and experiment and these methods have been concentrated upon a research into the cerebral changes which accompany perception, apper- ception and will, respectively. 11 These experiments, although elaborate, and becoming more elaborate, may be classed under three heads. (1) The investigation of simple physiological time, that is, when the subject is aware of the coming impression, but is ignorant just when it will take place. (2) Those in which even this element of ignorance is eliminated. (3) Those in which modifications are possible widely, because, for example, the subject does not know what the impression will be, or is unaware of the character of the stimulus in such a way that he does not know how precisely he will be called upon to register it. In combination, these experiments show, as Wundt infers, that the exact moment of appercipience is dependent upon the self-accommoda- tion of the subject, particularly in the matter of attention. Take the third case :
An indicator is kept moving at a uniform rate over a graduated scale, and so situated that the place of the needle can be clearly seen at each instant of time. The action of the same clock which moves the needle causes a sound at any moment, but in such a way that the subject of the experiment does not know when to expect it. With what position of the needle, now, will the sensa- tion of sound be combined? Will the sound be heard exactly when it occurs, as indicated by the needle; or later than its real time (" positive " lengthening) ; or earlier than its real time (" negative" lengthening) ? The result shows that one rarely hears the sound without either positive or negative displacement of it; but most frequently the lengthening is negative — that is, one believes one hears the sound before it really occurs as measured by the indicator."
In this connection, then, the fundamental problem of physiological
11 Cf. Cattell in Mind, XIIL, pp. 37 ff. (old series), and Titchener in ibid., I., pp. 206 ff. (new series).
12 " Elements of Physiological Psychology," Ladd, p. 488.