stop, but the opposite is the case. The apparent movement from the
vertical to the horizontal has to pass our fixation point and it seems
that we ought now to recognize clearly that there is nothing between
those two positions, that the intermediate phases of the movement are
lacking; and yet the experiment shows that under these circumstances we
frequently get the strongest impression of motion. If we use two
horizontal lines, the one above the other, we see, if the right time
interval is chosen, that the upper one moves downward toward the lower.
But we can introduce there a very interesting variation. If we make the
lower line, which appears objectively after the upper one, more intense,
the total impression is one which begins with the lower. We see first
the lower line moving toward the upper one which also approaches the
lower; and then follows the second phase in which both appear to fall
down to the position of the lower one. It is not necessary to go further
into details in order to demonstrate that the apparent movement is in no
way the mere result of an afterimage and that the impression of motion
is surely more than the mere perception of successive phases of
movement. The movement is in these cases not really seen from without,
but is superadded, by the action of the mind, to motionless pictures.

The statement that our impression of movement does not result simply
from the seeing of successive stages but includes a higher mental act
into which the successive visual impressions enter merely as factors is
in itself not really an explanation. We have not settled by it the
nature of that higher central process. But it is enough for us to see
that the impression of the continuity of the motion results from a
complex mental process by which the various pictures are held together
in the unity of a higher act. Nothing can characterize the situation
more clearly than the fact which has been demonstrated by many
experiments, namely, that this feeling of movement is in no way