In controlled association, as in free association, only one of the facts previously linked with the stimulus is recalled at a time; but while in free association the factors of frequency, recency and intensity of past linkage determine which of the many possible facts shall be recalled, in controlled association the additional factor of mental set is present and has a controlling influence in determining which fact shall be recalled. Thus, in an opposites test, the stimulus word "good" promptly calls up the pair "good--bad", because the mental set for opposites gives this response a great advantage over "good night" and other responses which may have a very strong linkage with the stimulus word. The mental set is itself a response to a stimulus. It is an inner response thrown into activity by some stimulus, such as the stimulus of being asked to give the opposites of a series of words that are presently to be shown or spoken. This inner response of getting ready for the task can be introspectively observed by a person who is new to this type of test. It may take the form of mentally running over examples of opposites--or whatever kind of responses are to be called for--or it may take the form of calling up some image or diagram or gesture that symbolizes the task. A visual image of the nose on the face may serve as a symbol of the part-whole relationship, a small circle inside a larger one may symbolize the relation of an object to a class of objects, and gesturing first to the right and then to the left may symbolize the relationship of opposites. But as the subject grows accustomed to a given task, these conscious symbols fade away, and nothing remains except a general "feeling of readiness" or of "knowing what you are {384} about". The mental set remains in force, however, and is no less efficient for becoming almost unconscious. Examples of Controlled Association Dwelling so long on the test for controlled association may have created the impression that this is a rather artificial and unusual type of mental performance; but in reality controlled association is a very representative mental process, and enters very largely into all forms of mental work. This is true in arithmetical work, for example. A pair of numbers, such as 8 and 3, has been linked in past experience with several responses; it means 83, it means 11, it means 5, and it means 24. But if you are adding, it means 11, and no other response occurs; if you are multiplying, it means 24, and only that response occurs. The mental set for multiplying facilitates the responses of the multiplication table and inhibits those of the addition table, while the mental set for adding does the reverse. Rapid adding or multiplying would be impossible without an efficient mental set. Thus in arithmetic, as in the tests, the mental set is an inner response to the _task_.