Page:Encyclopædia Britannica, Ninth Edition, v. 20.djvu/77

PSYCHOLOGY 65 successively, and this we have both in the persistence of primary memory-images and in the simultaneous reproduc- tion of longer or shorter portions of the memory -train. In a series thus secured there may be time-marks, though no time, and by these marks the series must be distin- guished from other simultaneous series. To ask which is first among a number of simultaneous presentations is unmeaning; one might be logically prior to another, but in time they are together and priority is excluded. Nevertheless after each distinct representation a, b, c, d there probably follows, as we have supposed, some trace of that movement of attention of which we are aware in passing from one presentation to another. In our present reminiscences we have, it must be allowed, little direct proof of this interposition, though there is strong indirect evidence of it in the tendency of the flow to follow the order in which the presentations were first attended to. With the movements themselves we are familiar enough, though the residua of such movements are not ordinarily conspicuous. These residua, then, are our temporal signs, and, together with the representations connected by them, constitute the memory-continuum. But temporal signs alone will not furnish all the pictorial exactness of the time-perspective. They give us only a fixed series ; but the working of obliviscence, by insuring a progressive variation in intensity and distinctness as we pass from one member of the series to the other, yields the effect which we call time -distance. By themselves such variations would leave us liable to confound more vivid repre- sentations in the distance with fainter ones nearer the present, but from this mistake the temporal signs save us ; and, as a matter of fact, where the memory-train is imperfect such mistakes continually occur. On the other hand, where these variations are slight and imperceptible, though the memory -continuum preserves the order of events intact, we have still no such distinct appreciation of comparative distance in time as we have nearer the present where these perspective effects are considerable. Bration, When in retrospect we note that a particular presenta- tion X has had a place in the field of consciousness, while a series of objects ABC D . . . have succeeded each other, then we may be said in observing this relation of the two to perceive the duration of X. And it is in this way that we do subjectively estimate longer periods of time. But first, it is evident that we cannot apply this method to indefinitely short periods without passing beyond the region of distinct presentation ; and, since the knowledge of duration implies a relation between distinguishable pre- sentations A B C D and X, the case is one in which the hypothesis of subconsciousness can hardly help any but those who confound the fact of time with the knowledge of it. - Secondly, if we are to compare different durations at all, it is not enough that one of them should last out a series A B C D, and another a series L M N ; we also want some sort of common measure of those series. Locke was awake to this point, though he expresses himself vaguely (Essay, ii. 14, 9-12). He speaks of our ideas succeeding each other "at certain distances not much unlike the images in the inside of a lantern turned round by the heat of a candle," and "guesses" that "this appear- ance of theirs in train varies not very much in a waking man." Now what is this "distance" that separates A from B, B from C, and so on, and what means have we of knowing that it is tolerably constant in waking life ? It is probably that the residuum of which we have called a temporal sign ; or, in other words, it is the movement of attention from A to B. But we must endeavour here to get a more exact notion of this movement. Everybody knows what it is to be distracted by a rapid succession of varied impressions, and equally what it is to be wearied by the slow and monotonous recurrence of the same im- pressions. Now these "feelings" of distraction and tedium owe their characteristic qualities to movements of atten- tion. In the first, attention is kept incessantly on the move : before it is accommodated to A, it is disturbed by the suddenness, intensity, or novelty of B; in the second, it is kept all but stationary by the repeated presentation of the same impression. Such excess and defect of sur- prises make one realize a fact which in ordinary life is so obscure as to escape notice. But recent experiments have set this fact in a more striking light, and made clear what Locke had dimly before his mind in talking of a certain distance between the presentations of a waking man. In estimating very short periods of time, of a second or less, indicated say by the beats of a metronome, it is found that there is a certain period for which the mean of a number of estimates is correct, while shorter periods are on the whole overestimated, and longer periods under- estimated. This we may perhaps take to be evidence of the time occupied in accommodating or fixing attention. Whether the " point of indifference " is determined by the rate of usual bodily movement, as Spencer asserts and Wundt conjectures, or conversely, is a question we need not discuss just now. But, though the fixation of atten- tion does of course really occupy time, it is probably not in the first instance perceived as time, i.e., as continuous " protensity," to use a term of Hamilton's, but as intensity. Thus, if this supposition be true, there is an element in our concrete time-perceptions which has no place in our abstract conception of time. In time conceived as physical there is no trace of intensity ; in time psychically experi- enced duration is primarily an intensive magnitude, witness the comparison of times when we are " bored " with others when we are amused. It must have struck every one as strange who has reflected upon it that a period of time which seems long in retrospect such as an eventful ex- cursion should have appeared short in passing ; while a period, on the contrary, which in memory has dwindled to a wretched span seemed everlasting till it was gone. But, if we consider that in retrospect length of time is repre- sented primarily and chiefly by impressions that have sur- vived, we have an explanation of one-half ; and in the intensity of the movements of attention we shall perhaps find an explanation of the other. What tells in retrospect is the series abode, &c. ; what tells in the present is the intervening t^t z t z , &c., or rather the original accommoda- tion of which these temporal signs are the residuum. For, as we have seen elsewhere, the intensity of a presentation does not persist, so that in memory the residuum of the most intense feeling of tedium may only be so many t's in a memory-continuum whose surviving members are few and uninteresting. But in the actual experience, say, of a wearisome sermon, when the expectation of release is continually balked and attention forced back upon a monotonous dribble of platitudes, the one impressive fact is the hearer's impatience. On the other hand, so long as we are entertained, attention is never involuntary, and there is no continually deferred expectation. Just as we are said to walk with least effort when our pace accords with the rate of swing of our legs regarded as pendulums, so in pastimes impressions succeed each other at the rate at which attention can be most easily accommodated, and are such that we attend willingly. We are absorbed in the present without being unwillingly confined to it ; not only is there no motive for retrospect or expectation, but there is no feeling that the present endures. Each im- pression lasts as long as it is interesting, but does not con- tinue to monopolize the focus of consciousness till attention to it is fatiguing, because uninteresting. In such facts, then, we seem to have proof that our perception of duration rests XX. 9