We may approach the same result also from experiments of very different kind.  If a flash of light at one point is followed by a flash at another point after a very short time, about a twentieth of a second, the two lights appear to us simultaneous.  The first light is still fully visible when the second flashes, and it cannot be noticed that the second comes later than the first.  If now in the same short time interval the first light moves toward the second point, we should expect that we would see the whole process as a lighted line at rest, inasmuch as the beginning and the end point appear simultaneous, if the end is reached less than a twentieth of a second after the starting point.  But the experiment shows the opposite result.  Instead of the expected lighted line, we see in this case an actual movement from one point to the other.  Again we must 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.