Page:Mind (New Series) Volume 9.djvu/17

PERCEPTION OP CHANGE AND DURATION. 3 the judgment presupposes both sounds as its conditions, it does not necessarily contain both as its constituents. Of course at the moment when the second sound occurs, it must occur in connexion with some after-effect of the first. But this after-effect need not be a memory image. It is sufficient to assume a physiological or psychical dis- position. And Schumann maintains that as a matter of fact this is all that experience guarantees. He says: "In comparing two notes, which follow one another at an interval of, say, two seconds, I am in general unable to detect the slightest trace of the first sensation when the second occurs. Other gentlemen have said the same thing in answer to my question. Yet others were not quite con- fident : but even they could not directly affirm that the prior sensation was actually present. When I observed sensa- tions which followed each other very rapidly, at intervals of i of a second for example, I could not frame any distinct judgment on the matter ; but at any rate I could not ascertain any persistence of the first sensation in conscious- ness." Schumann concludes that for psychical elements to form a whole, they need not be presented together. To "form a single whole" means to act as a whole, to operate as a whole in determining reproduction, judgment, and feel- ing. The effects of the whole are not equal to the sum of the effects of its elements : the whole complex has its own characteristic effects which depend only on the relations of its constituents. But there is no reason why such effects should not be produced by a complex of experiences which follow each other in time. Schumann next turns to temporal perception in the strict sense, in which succession and duration are expressly attended to. He takes first the case of a note heard for one second. According to the memory-image theory, in each successive moment during which the note endures there is a sensational experience, and each sensational experience persists in the form of a memory image. Thus the note gradually spreads itself out as time goes on. One layer of memory imagery supeqxises itself on another, so as to form a kind of duration block, and this is what is present to consciousness when we perceive a note of one second's duration. Schumann denies that he can detect anything of the sort by introspection. " For me," he says, " a tone-sensation of one second's dura- tion is a unity not really capable of further division, a unity which can give rise to a plurality of judgments judgments referring to intensity, pitch, timbre and temporal duration. If we are able to form an immediate judgment as to whether