an apparent 'association by similarity' to some
other form; there may be partial identity, in
which case the identical member of two groups
is first experienced with one and then with the
other, as the red of the sunset passing over into
the red of blood; or there may be sim])le con-
tiguity, the similar objects having stood together
in experience; or there may be an indirect asso-
ciation, such as we found above, where two
things stand in the same relation to a third, as
two objects to the name of the class to which
they belong.
On the other hand, 'contiguity' can be re- garded as an ex])lanation only when we think of it in terms of neural activity. It is true that we can state it in general )3syehological terms, saying that conscious connections once set up tend to persist, so that when a single item (sensation, fusion, perception) comes to consciousness, it tends to bring with it other items with which it has appeared before in consciousness. This for- mula, which may be regarded either as a law of habit — if fl-e think of the tendency to persist — or as a law of redintegration — if we think of its results — receives, however, its full signifi- cance only when we translate it into physiologi- cal terms and state it as a tendency in the nerv- ous S3'stem to do that which has Ijeen done be- fore. Neural tracts which have once been excit- ed together, tend to functionate together again; hence, if an excitation finds its way to one part of the brain, there is a tendency for the parts previously involved to be reexcited. Now, just what path an excitation will take in any particu- lar case we cannot foretell ; but we are able to name with a good deal of certainty the factors which contribute to association, i.e. to state the conditions under Avhich the tendency to form old connections is realized. At this point, ex- periment comes to our aid. It enables us to invite association under first one set of conditions and then another, and to watch the results. If a given process, o, lias formed several connec- tions, at various times, say, with d, s, and z, the one of these connections which is actually real- ized when a is brought to consciousness will depend upon the frequency of connection of each w-ith «, the recency of connection, the relative vividness of d, s, and :::, their relative positions in a series of processes, and their relative power to attract a wandering attention. The compara- tive values of these factors are determined by presenting to the observer simple stimuli (as colors, letters, or sounds), arranged in definite groups of two, and then asking him, when one member of a group is given again, to recall the other member which was previously given with it. The series are so arranged as to bring into prominence, one after another, the various fac- tors.
In investigating association, we have not only to give a quantitative measure of associability in terms of sensational elements; we must also study (1) the induence of other processes which chance to stand in consciousness, and (2) the nature of the associative consciousness; i.e. we must note what there is in mind when an asso- ciation is being made. The first of these prob- lems is illustrated by the overwrought traveler who 'colors' his association by his apprehen- siveness.or by the proof-reader who becomes inter- ested in his page and easily overlooks typo- graphical errors. The case is brouglit under ex- perimental conditions by giving an incentive to reproduction under the inliuence of a suggested idea. If the word 'part' is seen an instant, for example, just after the word 'wine' has been pronounced, it is likely to be read 'port.' The experiment shows us (a) within what wide limits an association may be influenced by the appropriate, momentary trend of consciousness, which thus becomes part-incentive, and (b) it also illustrates the last condition of association named above: the greater power to fascinate the attention and start associations pos.sessed by an idea when it bears a close resemblance to other contents of consciousness. The best way to solve our second problem — the analysis of associated contents — is to make the observer as much at his ease and as free from distracting influences as possible (seat him, say, in a dark room), and ask him to report in outline the associative train which follows from a word or sentence repeated to him. After this experience he is able to fill in the outline b- describing minutely the nature and the amount of the associative material, whether made up of visual, or auditory, or other imagery ; whether intense or weak ; whether clear or obscure ; whether full or thin, the number and arrangement of the ideas, the elements which carry the association and the changes in affective tone at the various stages of the jjrocess. One other point connected with tWk analysis of associated contents deserves to be noticed. There is a well-marked tendency toward economy in mental functions. The mind becomes expert, as does the body, so that after carrying through laboriously a sequence of processes for some time, the operation becomes gradually curtailed. We think our thoughts out (if, indeed, we do- not take them ready-made from our jjarents and neighbors), and then just use them as counters with a swift, shorthand review, without going through the trouble to 'think' or 'reason' every time we want to know. This mental ellipsis is common in the process leading to association. It is. as .John Stuart Jlill says, "like a stream which, breaking through its banks, cuts o(T a bend in its course." If we have the sequence aha given several times, we become alile to ]iass di- rectly to c from a without the intermediate link h being given at all : e.g. alarm — fire — Jnas, and' then alarm — loss. This is only another evidence] that contents in an association form a whole, and not a mere sequence of events. Some psychologists have gone so far as to say that associations may- be held together by a link which has never en- tered into consciousness at all. The evidence for this is not good, although it is a fact that., often the links are hard to find, either because, they are fleeting or becavise they are not at- tended to. A speaker's facial expression oi gesture may recall, for example, an event or place, even if the listener's attention is kepi on the discourse. Nevertheless, a full attention) is generally an aid to the forming of associa- tive relations.
Beyond the search for conditions of association and the analysis of association, much work has^ been done on the duration of association and of, its elements by the use of the reaction experiment. (See Action.) The time, for instance,] is taken for the associating of an object seen or' heard, with the idea of another object in the same class, as 'cat' — 'dog.' The time depends both upon the factors in the association (each
