conclude that the movement is more than the mere seeing of successive
positions, as in this case we see the movement, while the isolated
positions do not appear as successive but as simultaneous.

Another group of interesting phenomena of movement may be formed from
those cases in which the moving object is more easily noticed than the
impressions of the whole field through which the movement is carried
out. We may overlook an area in our visual field, especially when it
lies far to one side from our fixation point, but as soon as anything
moves in that area our attention is drawn. We notice the movement more
quickly than the whole background in which the movement is executed. The
fluttering of kerchiefs at a far distance or the waving of flags for
signaling is characteristic. All indicate that the movement is to us
something different from merely seeing an object first at one and
afterward at another place. We can easily find the analogy in other
senses. If we touch our forehead or the back of our hand with two blunt
compass points so that the two points are about a third of an inch
distant from each other, we do not discriminate the two points as two,
but we perceive the impression as that of one point. We cannot
discriminate the one pressure point from the other. But if we move the
point of a pencil to and fro from one point to the other we perceive
distinctly the movement in spite of the fact that it is a movement
between two end points which could not be discriminated. It is wholly
characteristic that the experimenter in every field of sensations,
visual or acoustical or tactual, often finds himself before the
experience of having noticed a movement while he is unable to say in
which direction the movement occurred.

We are familiar with the illusions in which we believe that we see
something which only our imagination supplies. If an unfamiliar printed