ng dark blue, the sound of a
trumpet a vivid red, etc. Each vowel and even each consonant may have
its own special color, which combine to give a complex color scheme
for a word. Numbers also may be colored. This colored hearing is the
commonest form of "synesthesia", which consists in responding to a
stimulus acting on one sense, by sensations belonging to a different
sense. Whether the persons so constituted as to respond in this way
are constituted thus by nature or by experience is uncertain, though
the best guess is that the extra sensations are images that have
become firmly attached to their substitute stimuli during early
childhood.

Free Association

Mental processes that depend on recall are called "associative
processes", since they make use of associations or linkages previously
formed. When some definite interest or purpose steers the associative
processes, we speak of "controlled association", contrasting this with
the "free association" that occurs in an idle mood, when one thought
simply calls up another with no object in view and no more than
fleeting desires to give direction to the sequence of thoughts.

_Revery_ affords the best example of free association. I {377} see my
neighbor's dog out of my window, and am reminded of one time when I
took charge of that dog while my neighbor was away, and then of my
neighbor's coming back and taking the dog from the cellar where I had
shut him up; next of my neighbor's advice with respect to an
automobile collision in which I was concerned; next of the stranger
with whom I had collided, and of the stranger's business address on
the card which he gave me; next comes a query as to this stranger's
line of business and whether he was well-to-do; and from there my
thoughts switch naturally to the high cost of living.

This is rather a drab, middle-aged type of revery, and youth might
show more life and color; but the linkages between one thought and the
next are typical of any revery. The linkages belong in the category of
"facts previously observed". I had previously observed the ownership
of this dog by my neighbor, and this observation linked the dog and
the neighbor and enabled the dog to recall the neighbor to my mind.
Most of the linkages in this revery are quite concrete, but some are
rather abstract, such as the connection between being well-to-do (or
not) and the high cost of living; but, concrete or abstract, they are
connections previously observed