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.