Psychology - Robert S. Woodworth (trending books to read TXT) 📗

are at any time, and especially in childhood and youth, a vast number of loose connections. These are too weak to operate singly, until they have coöperated in producing a response, and thus been individually strengthened, after which they may be able singly to produce the response.

The law of combination, then, as applied to learning, includes four points:

(a) A collection of stimuli may work together and arouse a single response.

(b) This is possible because of pre-existing loose linkage between the separate stimuli and the response.

(c) When any stimulus, working together with others, helps to arouse a response, its linkage with that response is strengthened by exercise.

(d) The linkage may be sufficiently strengthened so that a single stimulus can arouse the response without help from the other stimuli that were originally necessary.

Having now abundantly stated and reiterated the law of combination in the abstract, let us turn to concrete instances of learned reactions, and see how the law takes care of them. We have already classified a large share of all the concrete instances under a few main heads, as substitute stimulus, substitute response, combination (or association) of stimuli, and combination of responses. We shall presently find it possible to reduce these four classes to two, since the association of two objects, by virtue of which one of them later recalls the other, is a rather complicated case of substitute stimulus, while the combination of movements into a higher unit is a complicated case of substitute response.

[Footnote: To distinguish between "substitute stimulus" and "substitute response" is, in strict logic, like distinguishing between "inside out" and "outside in." Whenever there is a substitute stimulus there is also a substitute response, of course, since this stimulus, in being substituted for another, gets that other's response in place of its own original response; and in the same way, you can always find substitute stimulus in any instance of substitute response; for, in being substituted for another, a response gets that other's stimulus in place of its own original stimulus. For all that, the distinction between the two main cases of learning is of some importance, since sometimes the changed stimulus, and sometimes the changed response, is the interesting fact.]

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I. SUBSTITUTE STIMULUS EXPLAINED BY THE LAW OF COMBINATION

Here the response, without being itself essentially changed, becomes attached to a new stimulus. We distinguish two cases under the general head of substitute stimulus. In the one case, the substitute stimulus was originally extraneous, and unnecessary for arousing the response, while in the other case it was originally necessary as part of a team of stimuli that aroused the response.

A. Substitute Stimulus Originally Unnecessary for Arousing the Response 1. Conditioned reflex.

This is the very simplest case belonging under the law of combination. The dog that responded to the bell by a flow of saliva, after the bell plus a tasting substance had acted together on him time after time, is the typical instance; and another good instance is that of the little child who was "taught" to shrink from a rabbit by the sounding of a harsh noise along with the showing of the rabbit. [Footnote: See p. 303.] The explanation of all instances of conditioned reflex is the same. We have an effective stimulus acting, i.e., a stimulus strongly linked with the response; and we also have acting an ineffective stimulus, which gets drawn into the same reaction. The effective stimulus determines what response shall be made, and the other stimulus finds an outlet {402} into that response, being, as it seems, attracted towards the activated response, sucked into it. The weak linkage from the ineffective stimulus to the response, being thus used and strengthened, later enables this stimulus to arouse the response single-handed.

This sort of thing is best presented in a diagram. A full line in the diagram denotes a linkage strong enough to work alone, while a dotted line denotes a weak linkage. Letters stand for stimuli and responses. In the diagram for conditioned reflex, A is the original effective stimulus (the rasping noise in the instance of the child and the rabbit), and B is the ineffective stimulus (the sight of the rabbit). R is the shrinking response, linked strongly to the stimulus A and only weakly to the stimulus B, which has several other linkages fully as good as the linkage B-R. But A arouses the response R; and R, being thus activated, draws on B and brings the linkage B-R into use. After this has occurred a number of times, the linkage B-R has been so strengthened by repeated exercise that it can operate alone, so that the rabbit brings the shrinking response even in the absence of A, the noise.

Fig. 55.--Attachment of the substitute stimulus in the case of the conditioned reflex.

At first, the child shrinks from the noise, but, the rabbit being before his eyes, he incidentally shrinks from the rabbit as well. He really shrinks in response to all the stimuli acting on him at that moment. He shrinks from the whole situation. He makes a unitary response to the whole collection of contiguous stimuli, and thus exercises the linkage between each stimulus and their joint response. The {403} linkage between rabbit and shrinking is later strong enough to work alone. It is a clear case of the law of combination.

2. Learning the names of things.

A child who can imitate simple words that he hears is shown a penny and the word "penny" is spoken to him. To this combination of stimuli he responds by saying the word. This is primarily a response to the auditory stimulus, since the sight of the penny, though it might probably have aroused some response, and even some vocal response from the child, had no strong linkage with this particular vocal response. But the auditory stimulus determined the response, and attracted the visual stimulus into this particular channel of saying "penny". The linkage from the sight of the penny to the saying of this word being thus strengthened by exercise, the seen penny later gives the right vocal response, without any auditory stimulus to assist.

Fig. 56.--Linkage of a name to an object. The diagram is arranged to illustrate the formation of a linkage from the sight of the object to saying its name. A very similar diagram would illustrate the linkage from the name to the thought or image of the object. The acquiring of mental images seems to be essentially the same process as the acquiring of conditioned reflexes, and of names. (Figure text: object seen, various possible responses, name heard, name spoken)

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B. Substitute Stimulus Originally an Essential Member Of A Team of Stimuli That Aroused the Response 1. Observed grouping or relationship.

"Learning by observation" is a very important human accomplishment, and we found many evidences of its importance in our study of the process of memorizing. The facts observed, which assist memory so greatly, are usually relations or groups.

Fig. 57.--The formation of an association between two objects by observing their grouping or relationship. (Figure text: response of observing the Group A B, thought of Group A B)

Evidently the observation of a group of things is a response to a collection of stimuli, and could not originally be aroused by any one of the stimuli alone. The same is true of observing a relationship; the observation is a response to two things taken together, and not, originally, to either of the two things taken alone. In spite of this, a single one of the things may later call to mind the relationship, or the group; that is, it arouses the response originally made to the pair or group of stimuli. The single stimulus has been substituted for the team that originally aroused the response. Its linkage with the response has been so strengthened by exercise as to operate effectively without assistance.

For example, in learning pairs of words in a "paired {405} associates experiment", [Footnote: See p. 336.] the subject is apt to find some relation between the words forming a pair, even though they are supposed to be "unrelated words". When he has thus learned the pair, either of the words in it will recall the observed relation and the other word of the pair. Sometimes, after a long interval especially, the relation is recalled without the other word. One subject fixed the pair, "windy--occupy", by thinking of a sailor occupying a windy perch up in the ropes. Some weeks later, on being given the word "windy", he recalled the sailor on the perch, but could not get the word "occupy". That is, he made the same response to "windy" that he had originally made to "windy--occupy", but did not get the response completely enough to give the second word.

In the typical cases of association by contiguity when one object reminds us of another that was formerly experienced together with it, the law of combination comes in as just described. The two objects were observed to be grouped or related in some way, or some such unitary response was made to the two objects taken together, and this response became so linked to each of the objects that later a single one of them arouses this unitary response and recalls the other object. In the free association test, [Footnote: See p. 380.] the stimulus word "dimple" calls up the previously made response of seeing a dimple in a cheek, and so leads to the word "cheek". In a controlled association test, where opposites are required, the stimulus word "mythical" arouses the previously made observation of the antithesis of mythical and historical, and so leads to the motor response of saying the latter word.

[Footnote: When, however, this indirect linkage between stimulus and motor response is frequently exercised, short-circuiting takes place (see p. 338), and the stimulus word arouses the motor response directly. Short-circuiting follows the law of combination very nicely. Let a stimulus S arouse an idea I and this in turn a motor act M. S--I--M represents the linkages used. But undoubtedly there is a weak pre-existing linkage directly across from S to M, and this gets used to a slight degree, strictly according to the conditioned reflex diagram, with I playing the part of the effective stimulus in arousing M, and S the part of the originally ineffective stimulus. By dint of being exercised in this way, the linkage S--M becomes strong enough to arouse the motor response directly, and I is then very likely to be left out altogether.]

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2. Response by analogy and association by similarity.

When an object reminds me of a similar object, that is association by similarity. But suppose I actually take the object to be the similar object, and behave towards it accordingly; then my reaction is called "response by analogy". Once, when far from home, I saw a man whom I took to be an acquaintance from my home town, and stepped up to him, extending my hand. He did not appear very enthusiastic, and informed me that, in his opinion, I had made a mistake. This was response by analogy, but if I had simply said to myself that that man looked like my acquaintance, that would have been association by similarity. Really, association by similarity is the more complex response, for it involves response to the points of newness in the present object, as well as to the points of resemblance to the familiar object, whereas response by analogy consists simply in responding to the points of resemblance.

Response by analogy often appears in little children, as when they call all men "papa"' or as when they call the squirrel a "kitty" when first seen. If they call it a "funny kitty", that is practically association by similarity, since the word "funny" is a response to the points in which a squirrel is different from a cat, while the word "kitty" is