xperiments can be made. It is thus found that, if the field before
one eye is a plain color, while the other, of a different color, has
any little figure on it, this figure has a great advantage over the
rival plain color and stays in sight most of the time. Anything moving
in one field has a similar advantage, and a bright field has the
advantage over a darker one. Thus the same factors of advantage hold
good in binocular rivalry as in native attention generally.

A different kind of shifting appears in what is called "fluctuation of
attention". Make a light gray smudge on a white sheet of paper, and
place this at such a distance that the gray will be barely
distinguishable from the white {255} background. Looking steadily at
the smudge, you will find it to disappear and reappear periodically.
Or, place your watch at such a distance that its ticking is barely
audible, and you will find the sound to go out and come back at
intervals. The fluctuation probably represents periodic fatigue and
recovery at the brain synapses concerned in observing the faint
stimulus.

Shiftings of the fluctuation type, or of the rivalry type either, are
not to be regarded as quite the same sort of thing as the ordinary
shiftings of attention. The more typical movement of attention is
illustrated by the eye movements in examining a scene, or by the
sequence of ideas and images in thinking or dreaming. Rivalry and
fluctuation differ from this typical shifting of attention in several
ways:

(1) The typical movement of attention is quicker than the oscillation
in rivalry or fluctuation. In rivalry, each appearance may last for
many seconds before giving way to the other, whereas the more typical
shift of attention occurs every second or so. In fact, during a
rivalry or fluctuation experiment, you may observe thoughts coming and
going at the same time, and at a more rapid rate than the changes in
the object looked at. Attention does not really hold steady during the
whole time that a single appearance of an ambiguous figure persists.

(2) Rivalry shifts are influenced very little, if at all, by the
factor of momentary desire or interest, and are very little subject to
control.

(3) In rivalry, the color that disappears goes out entirely, and in
looking at a dot figure or ambiguous figure you get the same effect,
since the grouping or appearance that gives way to another vanishes
itself for the time being. But when, in exploring a scene with