o understand that each short jump occupies but a thirtieth to
a fiftieth {251} of a second, while the "fixation pauses" between
jumps last much longer, with the result that over ninety per cent. of
the time spent on a line of print is fixation time, and less than ten
per cent, is occupied in jumping from one fixation to the next. Now,
it has been found that nothing of any consequence is seen during the
eye jumps, and that the real seeing takes place only during the
fixations. The jump movement, therefore, is simply a means of passing
from one fixation to another with the least possible loss of time.

The eye sees an object distinctly only when at rest with respect to
the object. If the object is still, the eye must be still to see it
distinctly, and to see its different parts must fixate one after the
other, jumping from one part to another. But if the object is in
motion, the eye may still be able to see it distinctly by means of the
pursuit movement, which is a sort of moving fixation.

The Shifting of Attention

Eye movement affords a good picture of the mobility of attention.
Ordinarily the eye shifts frequently from one part of the field of
view to another. When simply exploring a scene, it shifts about in
what seems an indiscriminate way, though really following the
principle of deserting each object as soon as it has been examined,
and jumping to that other object which next has the advantage on
account of movement, brightness, color, definite form, or habit of
attention. In reading, however, the eye is governed by a definite
interest, and moves consecutively along the series of words, instead
of shifting irregularly about the page.

A moving object, or an object that is doing something, or even a
complex object that presents a number of parts to be examined in turn,
can hold the eye for some time. But it is almost impossible to hold
the eye fixed for any length of time on a simple, motionless,
unchanging object.

{252}

Attention is mobile because it is exploratory; it continually seeks
something fresh for examination. In the presence of a complex of
sights and sounds and touch stimuli, it tends to shift every second or
two from one part of the situation to another. Even if you are lying
in bed with your eyes closed, the movement of attention still appears
in the rapid succession of thoughts and images, and some shift usually
occurs as often as once a second.

A few simple experiments will serve to th