have done. Such a simple mental operation as the recognition of one of
the less common flowers, say a particular orchid, will vary in duration
according as we have or have not been recently forming an image of this
flower. The obvious explanation of this is that the mental image of an
object bears a very close resemblance to the corresponding percept,
differing from it, indeed, in degree only, that is to say, through the
fact that it involves no actual sensation. Here again we see illustrated
a general psychological law, namely, that what the mind has recently
done, it tends (within certain limits) to go on doing.

It is to be noticed, further, that the perception of a single object or
event is rarely an isolated act of the mind. We recognize and understand
the things that surround us through their relations one to another.
Sometimes the adjacent circumstances and events suggest a definite
expectation of the new impression. Thus, for example, the sound of a gun
heard during a walk in the country is instantly interpreted by help of
suggestions due to the previous appearance of the sportsman, and the act
of raising the gun to his shoulder. It may be added that the verbal
suggestions of others act very much like the suggestions of external
circumstances. If I am told that a gun is going to be fired, my mind is
prepared for it just as though I saw the sportsman.[10]

More frequently the effect of such surrounding circumstances is to give
an air of familiarity to the new impression, to shorten the interval in
which the required interpretative image is forthcoming. Thus, when
travelling in Italy, the visual impression answering to a ruined temple
or a bareheaded friar is construed much more rapidly than it would be
elsewhere, because of the attitude of mind due to the surrounding
circumstances. In all such cases the process of preperception connected
with a given impression is effected more or less completely by the