60 PSYCHOLOGY 10 seconds a considerable waning has taken place, and after 100 seconds all that is distinctive of the primary image has probably ceased. On the whole, then, it appears that the ordinary memory- image is a joint effect; it is not the mere residuum of changes in the presentation -continuum, but an effect of these only when there has been some concentration of attention upon them. It has the form of a percept, but is not constituted of " revived impressions," for the essential marks of impressions are absent ; there is no localization or projection, neither is there the motor adaptation, nor the tone of feeling, incident to the reception of impressions. Ideas do not reproduce the intensity of these original con- stituents, but only their quality and complication. What we call the vividness of an idea is of the nature of inten- sity, but it is an intensity very partially and indirectly determined by that of the original impression ; it depends much more upon the state of the memory-continuum and the attention the idea receives. The range of vividness in ideas is probably comparatively small ; what are called variations in vividness are often really variations in dis- tinctness and completeness. 1 Where we have great in- tensity, as in hallucinations, primary presentations may be reasonably supposed to enter into the complex. It is manifest that the memory-continuum has been in some way formed out of or differentiated from the pre- sentation-continuum by the movements of attention, but the precise connexion of the two continua is still very difficult to determine. We see perhaps the first distinct step of this evolution in the primary memory- image : here there has been no cessation in presentation and yet the characteristic marks of the impression are gone, so much so, indeed, that superposition without "fusion" with an exactly similar impression is possible. In this manner we . seem to have several primary images in the field of consciousness together, as when we cBUnt up the strokes of the clock after it has ceased striking. But, though the image thus first arises in the field of conscious- ness as a sort of ajroppoia. or emanation from the presenta- tion-continuum, its return (at which stage it first becomes a proper re-presentation) is never determined directly and solely by a second presentation like that which first gave it being. Its "revival" is not another birth. With a second impression exactly like the first we should have assimilation or simple recognition an identity of the in- discernible which precludes the individual distinctness required in representation. But how, then, was this dis- tinctness in the first instance possible in the series of primary images just referred to as being due to the re- petition of the same presentation 1 Seemingly to differ- ences in the rest of that field of consciousness in which each in turn occurred and to some persistence of these differences. If the whole field which the second impres- sion entered had been just like the field of the first it is hard to see what ground for distinctness there would have been. When such second impression does not occur till after the primary memory-image has ceased, a representa- tion is still possible provided the new impression can reinstate sufficient of the mental framing of the old to give the image individual distinctness. This is really what happens in what is ordinarily called " association by similarity," similarity, that is, in the midst of some diversity. Our inquiry into the connexion between pre- sentations and representations has thus brought us to the general consideration of mental association. As we have seen that there is a steady transition from percept to image, so, if space allowed, the study of hallucinations might make clear an opposite and abnormal process the passage, that is to say, of images into percepts, for such, to all intents and purposes, are hallucinations of perception, psychologically regarded. Mental Association and the Memory-continuum. Only a very brief treatment of this important subject Ass is permissible here, as it has already been handled at length ti( under ASSOCIATION OF IDEAS (q.v.). Great confusion has sini been occasioned, as we have seen incidentally, by the lax J U n use of the term "association"; this confusion has been in- me) creased by a further laxity in the use of the term " associa- tion by similarity." In so far as the similarity amounts to identity, as in assimilation, we have a process which is more fundamental than association by contiguity, but then it is not a process of association. Yet, when the re- viving presentation is only partially similar to the pre- sentation revived, the nature of the association does not appear to differ from that operative when one "contiguous" presentation revives another. In the one case we have, say, a b x recalling a b y and in the other a b c recalling def. ^ Now anybody who will reflect must surely see that the similarity between a b x and a b y, as distinct from the identity of their partial constituent a b, cannot be the means of recall; for this similarity is nothing but the state of mind to be studied presently which results when a b x and a b y, having been recalled, are in con- sciousness together and then compared. But, if a b, having concurred with y before and being now present in a b x, again revives y, the association, so far as that goes, is manifestly one of contiguity, albeit the state of mind im- mediately incident as soon as the revival is complete be what Dr Bain loves to style "the flash of similarity." So far as the mere revival itself goes, there is no more simi- larity in this case than there is when a b c revives def. For the very a b c that now operates as the reviving pre- sentation was obviously never in time contiguous with the def that is revived; if all traces of previous experiences of a b c were obliterated there would be no revival. In other words, the a b c now present must be "automatically asso- ciated," or, as we prefer to say, must be assimilated to those residua of a b c which were " contiguous " with d ef, before its representation can occur. And this, and nothing more than this, we have seen, is all the " similarity " that could be at work when a b x " brought up " a b y. On the whole, then, we may assume that the onlyconti principle of association we have to examine is the so-called guity "association by contiguity, "which, as ordinarily formulated, ex P lf ' runs : Any presentations whatever, which are in conscious- ness together or in close succession, cohere in such a way that when one recurs it tends to revive the rest, such tendency increasing with the frequency of the conjunction. But such a statement is liable to all the objections already urged against what we may call atomistic psychology. Pre- sentations do not really crowd into Mansoul by the avenues of Eyegate, Eargate, &c., there to form bonds and unions as in Bunyan's famous allegory. It has been often con- tended that any investigation into the nature of association must be fruitless. 2 But, if association is thus a first princi- ple, it ought at least to admit of such a statement as shall remove the necessity for inquiry. So long, however, as we are asked to conceive presentations originally distinct and isolated becoming eventually linked together, we shall naturally feel the need of some explanation of the process, for neither the isolation nor the links are clear, not the isolation, for we can only conceive two presentations sepa- rated by other presentations intervening ; nor the links, unless these are also presentations, and then the difficulty recurs. But, if for contiguity we substitute continuity and regard the associated presentations as parts of a new con- tinuum, the only important inquiry is how this new whole was first of all integrated. 3 So Hume, Treatise of Human Nature, pt. i. 4 (Green and Grose's ed., p. 321); also Lotze, Metaphysik, 1st ed., p. 526.
