word is exposed to our eye for the twentieth part of a second, we
readily substitute a familiar word with similar letters. Everybody knows
how difficult it is to read proofs. We overlook the misprints, that is,
we replace the wrong letters which are actually in our field of vision
by imaginary right letters which correspond to our expectations. Are we
not also familiar with the experience of supplying by our fancy the
associative image of a movement when only the starting point and the end
point are given, if a skillful suggestion influences our mind. The
prestidigitator stands on one side of the stage when he apparently
throws the costly watch against the mirror on the other side of the
stage; the audience sees his suggestive hand movement and 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