the
disappearance of the watch and sees twenty feet away the shattering of
the mirror. The suggestible spectator cannot help seeing the flight of
the watch across the stage.

The recent experiments by Wertheimer and Korte have gone into still
subtler details. Both experimenters worked with a delicate instrument in
which two light lines on a dark ground could be exposed in very quick
succession and in which it was possible to vary the position of the
lines, the distance of the lines, the intensity of their light, the time
exposure of each, and the time between the appearance of the first and
of the second. They studied all these factors, and moreover the
influence of differently directed attention and suggestive attitude. If
a vertical line is immediately followed by a horizontal, the two
together may give the impression of one right angle. If the time between
the vertical and the horizontal line is long, first one and then the
other is seen. But at a certain length of the time interval, a new
effect is reached. We see the vertical line falling over and lying flat
like the horizontal line. If the eyes are fixed on the point in the
midst of the angle, we might expect that this movement phenomenon would
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