Modern Criticism.—Of recent years the associationist theory has been subjected to searching criticism, and it has been maintained by many writers that the laws are both unsatisfactorily expressed and insufficient to explain the facts. Among the most vigorous and comprehensive of these investigations is that of F.H. Bradley in his Principles of Logic (1883). Having admitted the psychological fact of mental association, he attacks the theories of Mill and Bain primarily on the ground that they purport to give an account of mental life as a whole, a metaphysical doctrine of existence. According to this doctrine, mental activity is ultimately reducible to particular feelings, impressions, ideas, which are disparate and unconnected, until chance Association brings them together. On this assumption the laws of Association naturally emerge in the following form:—(1) The law of Contiguity.—“Actions, sensations and states of feeling, occurring together or in close connexion, tend to grow together, or cohere, in such a way that, when any one of them is afterwards presented to the mind, the others are apt to be brought up in idea” (A. Bain, Senses and Intellect, p. 327). (2) The law of Similarity.—“Present actions, sensation, thoughts or emotions tend to revive their like among previous impressions or states” (A. Bain, ibid. 457. Compare J.S. Mill, Logic, ii. p. 440, 9th ed.). The fundamental objection to (1) is that ideas and impressions once experienced do not recur; they are particular existences, and, as such, do not persevere to recur or be presented. So Mill is wrong in speaking of two impressions being “frequently experienced.” Bradley claims thus to reduce the law to “When we have experienced (or even thought of) several pairs of impressions (simultaneous or successive), which pairs are like one another; then whenever an idea occurs which is like all the impressions on one side of these pairs, it tends to excite an idea which is like all the impressions on the other side.” This statement is destructive of the title of the law, because it appears that what were contiguous (the impressions) are not associated, and what are associated (the ideas) were not contiguous; in other words, the association is not due to contiguity at all.
Proceeding to the law of Similarity (which in Mill’s view is at the back of association by contiguity), and having made a similar criticism of its phrasing, Bradley maintains that it involves an even greater absurdity; if two ideas are to be recognized as similar, they must both be present in the mind; if one is to call up the other, one must be absent. To the obvious reply that the similarity is recognized ex post facto, and not while the former idea is being called up, Bradley replies simply that such a view reduces the law to the mere statement of a phenomenon and deprives it of any explanatory value, though he hardly makes it clear in what sense this necessarily invalidates the law from a psychological point of view. He further points out with greater force that in point of fact mere similarity is not the basis of ordinary cases of mental reproduction, inasmuch as in any given instance there is more difference than similarity between the ideas associated.
Bradley himself bases association on identity plus contiguity:—“Any part of a single state of mind tends, if reproduced, to re-instate the remainder,” or “any element tends to reproduce those elements with which it has formed one state of mind.” This law he calls by the name “redintegration,” understood, of course, in a sense different from that in which Hamilton used it. The radical difference between this law and those of Mill and Bain is that it deals not with particular units of thoughts but with universals or identity between individuals. In any example of such reproduction the universal appears in a particular form which is more or less different from that in which it originally existed.
Psychophysical Researches.—Bradley’s discussion deals with the subject purely from the metaphysical side, and the total result practically is that association occurs only between universals. From the point of view of empirical psychologists Bradley’s results are open to the charge which he made against those who impugned his view of the law of similarity, namely that they are merely a statement—not in any real sense an explanation. The relation between the mental and the physical phenomena of association has occupied the attention of all the leading psychologists (see [Psychology]). William James holds that association is of “objects” not of “ideas,” is between “things thought of”—so far as the word stands for an effect. “So far as it stands for a cause it is between processes in the brain.” Dealing with the law of Contiguity he says that the “most natural way of accounting for it is to conceive it as a result of the laws of habit in the nervous system; in other words to ascribe it to a physiological cause.” Association is thus due to the fact that when a nerve current has once passed by a given way, it will pass more easily by that way in future; and this fact is a physical fact. He further seeks to maintain the important deduction that the only primary or ultimate law of association is that of neural habit.
The objections to the associationist theory are summed up by G.F. Stout (Analytic Psychol., vol. ii. pp. 47 seq.) under three heads. Of these the first is that the theory as stated, e.g. by Bain, lays far too much stress on the mere connexion of elements hitherto entirely separate; whereas, in fact, every new mental state or synthesis consists in the development or modification of a pre-existing state or psychic whole. Secondly, it is quite false to regard an association as merely an aggregate of disparate units; in fact, the form of the new idea is quite as important as the elements which it comprises. Thirdly, the phraseology used by the associationists seems to assume that the parts that go to form the whole retain their identity unimpaired; in fact, each part or element is ipso facto modified by the very fact of its entering into such combination.
The experimental methods now in vogue have to a large extent removed the discussion of the whole subject of association of ideas, depending in the case of the older writers on introspection, into a new sphere. In such a work as E.B. Titchener’s Experimental Psychology (1905), association is treated as a branch of the study of mental reactions, of which association reactions are one division.
Bibliography.—See [Psychology]; and the works of Bradley, Stout, and James, above quoted, and general works on psychology: articles in Mind (passim); A. Bain, Senses and Intellect (4th ed., 1894), and in Mind, xii. (1887) pp. 237-249; John Watson, An Outline of Philosophy (1898); H. Höffding, Hist. of Mod. Philos. (Eng. trans., Lond., 1900), Psychologie in Umrissen auf Grundlage der Erfahrung (2nd ed., Leipzig, 1893); Jas. Sully, The Human Mind (1892), and Outlines of Psych. (Lond., 1892); E.B. Titchener, Outline of Psych. (New York, 1896), and in his trans. of O. Külpe’s Outlines of Psych. (New York, 1895,); Jas. Ward in Mind, viii. (1883), xii. (1887), new series ii. (1893), iii. (1894); G.T. Ladd, Psychology, Descriptive and Explanatory (Lond., 1894); C.L.C. Morgan, Introd. to Comparative Psych. (Lond., 1894); W. Wundt, Princip. of Physiol. Psych. (Eng. trans., 1904), Human and Animal Psych. (Eng. trans., 1894), pp. 282-307; Outlines of Psych. (Eng. trans., 1897); E. Claparède, L’Association des idées (1903). For associationism in Greek philosophy see J.I. Beare, Greek Theories of Elementary Cognition (Oxford, 1906), part iii. §§ 14, 43 seq.
[1] There are, however, distinct anticipations of the theory in Plato (Phaedo), as part of the doctrine of ἀνάμνησις; thus we find the idea of Simmias recalled by the picture of Simmias (similarity), and that of a friend by the sight of the lyre on which he played (contiguity).