Page:Encyclopædia Britannica, Ninth Edition, v. 20.djvu/73

To ascertain this point we must examine each of the two leading divisions of contiguous association that of simul- ' taneous presentations and that of presentations occurring in close succession. The last, being the clearer, may be taken first. In a series of associated presentations, A B C D E, such as the movements made in writing, the words of a poem learned by heart, or the simple letters of the alphabet themselves, we find that each member recalls its successor but not its predecessor. Familiar as this fact is, it is not perhaps easy to explain it satisfactorily. Since C is associated both with B and D, and apparently as in- timately with the one as with the other, why does it revive the later only and not the earlier 1 B recalls C ; why does not C recall B 1 We have seen that any reproduction at all of A or B or C depends primarily upon its having been the object of special attention so as to occupy at least momentarily the focus of consciousness. Now we can in the first instance only surmise that the order in which they are reproduced is determined by the order in which they were thus attended to when first presented. The next question is whether the association of objects simul- taneously presented can be resolved into an association of objects successively attended to. Whenever we try to recall a scene we saw but for a moment there are always a few traits that recur, the rest being blurred and vague, instead of the whole being revived in equal distinctness or indistinctness. On seeing the same scene a second time our attention is apt to be caught by something un- noticed before, as this has the advantage of novelty ; and so on, till we have " lived ourselves into " the whole, which may then admit of simultaneous recall. Dr Bain, who is rightly held to have given the best ex- position of the laws of association, admits something very like this in saying that " coexistence is an artificial growth formed from a certain peculiar class of mental successions." But, while it is easy to think of instances in which the associated objects were attended to suc- cessively, and we are all perfectly aware that the surest not to say the only way to fix the association of a number of objects is by thus concentrating attention on each in turn, it seems hardly possible to mention a case in which attention to the associated objects could not have been successive. In fact, an aggregate of objects on which attention could be focused at once would be already associated. The only case, then, that now remains to be considered is that to take it in its simplest form of two primary presentations A and X, parts of different special continua or distinct i.e., non-adjacent parts of the same, and occupying the focus of consciousness in immediate succes- sion. This constitutes their integration ; for the result of this occupation may be regarded as a new continuum in which A and X become adjacent parts. For it is characteristic of a continuum that an increase in the intensity of any part leads to the intenser presentation of adjacent parts ; and in this sense A and X, which were not originally continuous, have come to be so. We have here, then, some justification for the term secondary or memory-continuum when applied to this continuous series of representations to distinguish it from the primary or presentation -continuum from which its constituents are derived. The most important peculiarity of this con- tinuum, therefore, is that it is a series of representations integrated by means of the movements of attention out of the differentiations of the primary or presentation- continuum, or rather out of so much of these differentia- tions as pertain to what we know as the primary memory- image. These movements of attention, if the phrase may be allowed, come in the end to depend mainly upon in- terest, but at first appear to be determined entirely by 61 mere intensity. 1 To them it is proposed to look for that continuity which images lose in so far as they part with the local signs they had as impressions and cease to be either localized or projected. Inasmuch as it is assumed that these movements form the connexion between one re- presentation and another in the memory-train they may be called "temporal signs." 2 The evidence for their ex- istence can be more conveniently adduced presently; it must suffice to remark here that it consists almost wholly of facts connected with voluntary attention and the volun- tary control of the flow of ideas, so that temporal signs, unlike local signs, are fundamentally motor and not sensory. And, unlike impressions, representations can have each but a single sign, 3 the continuum of which, in contrast to that of local signs, is not rounded and com- plete but continuously advancing. But in saying this we are assuming for a moment that the memory-continuum forms a perfectly single and un- broken train. If it ever actually became so, then, in the absence of any repetition of old impressions and apart from voluntary interference with the train, consciousness, till it ceased entirely, would consist of a fixed and mechanical round of images. Some approximation to such a state is often found in uncultured persons who lead uneventful lives, and still more in idiots, who can scarcely think at all. In actual fact, however, the memory-train is liable to Oblivis- change in two respects, which considerably modify its cence - structure, viz., (1) through the evanescence of some parts, and (2) through the partial recurrence of like impressions, which produces reduplications of varying amount and extent in other parts. As regards the first, we may infer that the waning or sinking towards the threshold of con- sciousness which we can observe in the primary mental image continues in subconsciousness after the threshold is past. For the longer the time that elapses before their revival the fainter, the less distinct, and the less complete are the images when revived, and the more slowly they rise. All the elements of a complex are not equally revivable, as we have seen already : tastes, smells, and organic sensations, though powerful as impressions to revive other images, have little capacity for ideal repro- duction themselves, while muscular movements, though perhaps of all presentations the most readily revived, do not so readily revive other presentations. Idiosyncrasies are, however, frequent ; thus we find one person has an exceptional memory for sounds, another for colours, another for forms. Still it is in general true that the most intense, the most impressive, and the most interesting presentations persist the longest. But the evanescence, which is in all cases comparatively rapid at first, deepens sooner or later into real or apparent oblivion. In this manner it comes about that parts of the memory-continuum lose all distinct- ness of feature and, being without recognizable content, 1 This connexion of association with continuous movements of atten- tion makes it easier to understand the difficulty above referred to, viz. that in a series A B C D . . . B revives C but not A , and so on a diffi- culty that the analogy of adhesiveness or links leaves unaccountable. To ignore the part played by attention in association, to represent the memory-continuum as due solely to the concurrence of presentations, is perhaps the chief defect of the associationist psychology, both Eng- lish and German. Mr Spencer's endeavour to show "that psychical life is distinguished from physical life by consisting of successive changes only instead of successive and simultaneous changes" (Prin- ciples of Psychology, pt. iv. ch. ii., in particular pp. 403, 406) is really nothing but so much testimony to the work of attention in forming the memory - continuum, especially when, as there is good reason to do, we reject his assumption that this growing seriality is physically determined. 2 A term borrowed from Lotze (Meiaphysik, 1st ed., p. 295), but the present writer is alone responsible for the sense here given to it and the hypothesis in which it is used. 3 Apart, that is to say, of course, from the reduplications of the memory-train spoken of below.