These phenomena are also explicable from the influence of the sensational and affective changes. An impression distinguished from the rest, demands a change in the [p. 151] course of the sensations, and especially of the feelings, preceding its apprehension, for there must be a more intense strain of expectation and a, correspondingly stronger feeling of relief or satisfaction. The feeling of expectation lengthens the interval preceding the impression, the feeling of relief that following. The case is different when the whole series is made up at one time of weak impressions, and at another of strong ones. In order to perceive a weak impression we must concentrate our attention upon it snore. The sensations of tension and the accompanying feelings are, accordingly, more intense, as may be easily observed, for weaker beats than for stronger ones. Here too, then, the different intensifies of the subjective elements that give rise to them are reflected in the differences between temporal ideas. The effect is, therefore, not only lost, but even reversed, when we compare not weak with strong but strong with still stronger beats.
9. The tendency found in the case of rhythmical touch-ideas for at least two like periods to unite and form a regular metrical unit shows itself in auditory ideas also, only in a much more marked degree. In tactual movements, where the sensations that limit the single periods are under the influence of the will, this tendency to form a rhythmical series shows itself in the actual alternation of weaker and stronger impressions. With auditory sensations, on the other hand, where the single impressions can be dependent only on external conditions, and are, therefore, objectively exactly alike, this tendency may lead to the following characteristic illusion. In a series of beats which are exactly alike in intensity and are separated by equal periods of time, certain single beats, occurring at regular intervals, are always heard as stronger than the others. The time that most frequently arises when there is nothing to determine it, is the 2/8-time, that is, the regular alternation of arses and theses. A slight [p. 152] modification of this, the 3/8-time, where two unaccented follow one accented beat, is also very common. This tendency to mark time can be overcome only by an effort of the will, and then only for very fast or very slow rates, where, from the very nature of the series, the limits of rhythmical perception are nearly reached.
For medium rates, which are especially favorable to the rise of rhythmical ideas, a suppression of this tendency for any length of time is hardly possible. If the effort is made to unite as many impressions as possible in a unitary time-idea, the phenomena become more complicated. We have accents of different degrees which alternate in regular succession with unaccented members of the series and thus, through the resulting divisions of the whole into groups, umber of impressions that may be comprehended in a single idea is considerably increased. The presence of two different grades of accent gives 3/4-time and 5/8-time, the presence of three grades gives 4 /4-time and 6/4-time, and as forms with three feet we have 9/8-time and 12/8-time. More than three grades of accentuation or, when the unaccented note is counted, more than four grades of intensity, are not to be found in either musical or poetical rhythms, nor can we produce more by voluntarily formation of' rhythmical ideas. Obviously, these three grades of accentuation mark the limits of the possible complexity of temporal ideas, in a way analogous to that in which the maximal number of included beats (§15, 6) marks the limits of their length.
The phenomenon of subjective accentuation and its influence on the sensation of rhythms, shows clearly that temporal ideas, like spacial ideas, are not derived from objective impressions alone, but that there are connected with these, subjective elements, whose character determines the apprehension of the objective impressions. The primary cause [p.153] of the accentuation of a particular beat is always to be found in the increased intensity of the preceding and concomitant feelings and sensations of movement. This increase in the intensity of the subjective elements is then carried over to the objective impression, and makes the latter also seem more intense. The strengthening of the subjective elements may be voluntary, through the increase of the muscular strain which produces sensations of movement, and in this way, finally results in a corresponding increase in the feelings of expectation; or this strengthening may take place without volition, when the effort to perceive a number of impressions together brings about an immediate articulation of the temporal idea through the corresponding subjective sensational and affective variations. C. GENERAL CONDITIONS FOR TEMPORAL IDEAS.
10. If we seek to account for the rise of temporal ideas on the basis of the phenomena just discussed, and of the regular combination of subjective sensational and affective elements with objective impressions, as it is there apparent; we must start with the fact that a sensation thought of by itself, can no more have temporal that it could have spacial attributes. Position in time can be possible only when single psychical elements enter into certain characteristic relations with other such elements. This condition of the union of a number of psychical elements holds for temporal ideas just as much as for those of space, but the kind of union is characteristic, and essentially different from that in space-ideas.