s the kind studied by Mr. Thorndike in animals, where a
certain stimulus is associated with a certain act. This is the sort
which is taught to soldiers in drilling, for example. In such a case
there need not be anything mental, but merely a habit of the body.
There is no essential distinction between association and habit, and the
observations which we made concerning habit as a mnemic phenomenon are
equally applicable to association.

(d) NON-SENSATIONAL ELEMENTS IN PERCEPTION.--When we perceive any object
of a familiar kind, much of what appears subjectively to be immediately
given is really derived from past experience. When we see an object, say
a penny, we seem to be aware of its "real" shape we have the impression
of something circular, not of something elliptical. In learning to draw,
it is necessary to acquire the art of representing things according
to the sensation, not according to the perception. And the visual
appearance is filled out with feeling of what the object would be like
to touch, and so on. This filling out and supplying of the "real" shape
and so on consists of the most usual correlates of the sensational core
in our perception. It may happen that, in the particular case, the real
correlates are unusual; for example, if what we are seeing is a
carpet made to look like tiles. If so, the non-sensational part of our
perception will be illusory, i.e. it will supply qualities which the
object in question does not in fact have. But as a rule objects do
have the qualities added by perception, which is to be expected,
since experience of what is usual is the cause of the addition. If our
experience had been different, we should not fill out sensation in
the same way, except in so far as the filling out is instinctive,
not acquired. It would seem that, in man, all that makes up space
perception, including the correlation of sight and touch and so on, is
almost entirely acquired. In that case there is a large mnemic element
in all the common perceptions by means of which we handle common
objects. And, to take another kind of instance, imagine what our
astonishment would be if we were to hear a cat bark or a dog mew. This
emotion would be dependent upon past experience, and would therefore be
a mnemic phenomenon according to the definition.

(e) MEMORY AS KNOWLEDGE.--The kind of memory of which I am now speaking
is definite knowledge of some past event in one's own experience.
From time to time we remember