12. By introducing special conditions we may make sensorial and muscular reactions the starting points for the study of the development of volitions in two different directions. Sensorial reactions furnish the means of passing from simple to complex volitions because we can in this case easily insert different psychical processes between the perception of the impression and the execution of the reaction. Thus we have a voluntary act of relatively simple character when we allow an act of cognition or discrimination to follow the perception of the impression and then let the movement depend on this second process. In this case not the immediate impression but the idea that results from the act of cognition or discrimination is the motive for the act to be performed. This motive is only one of a greater or smaller number of equally possible motives that could have come up in place of it; as a result the reaction-movement takes on the character of a voluntary act. In fact, we may [p. 200] observe clearly the feeling of resolution antecedent to the act and also the feelings preceding that and connected with the perception of the impression. This is still more emphatically the case, and the succession of ideational and affective processes is at the same time more complicated, when we bring in still another psychical process, as, for example, an association, to serve as the decisive motive for the execution of the movement. Finally, the voluntary process becomes one of choice when, in such experiments, the act is not merely influenced by a plurality of motives in such a way that several must follow one another before one determines the act, but when, in addition to that, one of a number of possible different acts is decided upon according to the motive presented. This takes place when preparations are made for different movements, for example, one with the right, another with the left hand, or one with each of the ten fingers, and the condition is prescribed for each movement that an impression of a particular quality shall serve as its motive, for example, the impression blue for the right hand, red for the left.
13. Muscular reactions, on the contrary, may be used follow out the retrogradation of volitional acts to reflex movement. In this form of reaction the preparatory expectation is directed entirely towards the external act, so that a voluntary inhibition or execution of the act in accordance with the special character of the impression, that is, a transition from simple to complex acts of will, is in this case impossible.
On the other hand, it is easy by practice so to habituate one's self to the invariable connection of an impression and a particular movement, that the process perception fades out more and more or takes place the motor impulse, and finally the movement becomes like a reflex movement. This reduction of volition to [p. 201] mechanical process, which in the case of sensorial reactions is never possible from the very nature of their conditions, shows itself in the shortening of the objective time to that observed for pure reflexes, and in the subjective coincidence in point of time of impression and reaction, while the characteristic feeling of resolution gradually disappears entirely.
13a. The chronometric experiments familiar in experimental psychology under the name of "reaction-experiments", are important for two reasons: first, as aids in the analysis of volitional processes, and secondly, as means for the investigation of the temporal course of psychical processes in general. This twofold importance of reaction-experiments reflects the central importance of volitions. On the one hand, the simpler processes, feelings, emotions, and their related ideas, are components of a complete volition; on the other, all possible forms of the interconnection of psychical compounds may appear as components of a volition. Volitional processes are, consequently, an appropriate transition to the interconnection between psychical compounds to be discussed in the next chapter.
For a "reaction-experiment" which is to be the basis of an analysis of a volitional process or any of its component psychical processes, we must have first of all exact and sufficiently fine (reading with exactness to 1/1000 sec.) chronometric apparatus (electric clock or graphic register). The apparatus must be so arranged that we can determine exactly the moment at which the stimulus acts and that at which the subject reacts.
This can be accomplished by allowing the stimulus itself (sound, light, or tactual stimulus) to close an electric current that sets an electric clock reading to 1/1000 sec., in motion, and then allowing the observer, by means of a simple movement of the hand which raises a telegraph-key, to break the current again at the moment in which he apprehends the stimulus.
In this way we may measure simple reactions varied in different ways (sensorial and muscular reactions, reactions with or without preceding signals), or we may bring into the process various other psychical acts (discriminations, cognitions, associations, selective processes) which may be regarded either as motives for the volition [p. 202] or as components of the general interconnection of psychical compounds. A simple reaction always includes, along with the volitional process, purely physiological factors (conduction of the sensory excitation to the brain and of the motor excitation to the muscle). If, now, we insert further psychical processes (discriminations, cognitions, associations, acts of choice), a modification which can be made only when sensorial reactions are employed, the duration of clearly definable psychical processes may be gained by subtracting the interval found for simple reactions from those found for the compound reactions. In this way it has been determined that the time required for the cognition and for the discrimination of relatively simple impressions (colors, letters, short words) is 0.03 - 0.05"; the time for choice between two movements (right and left hand) is 0.06", between ten movements,the ten fingers) 0.4", etc. As already remarked, the value of these figures is not their absolute magnitude, but rather their utility as cheeks for introspection, while at the same time we may apply this introspective observation to processes subject to conditions which are prescribed with exactness by means of experimental methods and which may therefore be repeated at pleasure.
[ 1] The reaction-times for sensations of taste, smell, temperature, and pain are not reckoned in the figures given. They are all longer. The differences are, however, obviously to be attributed to pure physiological conditions (slow transmission of the stimulation to the nerve-endings, and in the case of pain slower central conduction), so that they are of no interest for psychology.