From the standpoint of education what we neglect is quite as important
as what is selected for attention.

The breadth of a person's attention, _i.e.,_ the number of lines along
which attention is possible, must vary with age and experience. The
younger or the more immature an individual is, the greater the number of
different lines to which attention is given. It is the little child
whose attention seems omnivorous, and it is the old person for whom
situations worthy of attention have narrowed down to a few lines. This
must of necessity be so, due to the interrelation of attention and
neglect. The very fact of continuing to give attention along one line
means less and less ability and desire to attend along other lines.

The question as to how many things, whether objects or ideas, can be
attended to at the same time, has aroused considerable discussion. Most
people think that they are attending to several things, if not to many,
at the same second of consciousness. Experiments show that if four or
five unrelated objects, words, or letters be shown to adults for less
than one quarter of a second, they can be apprehended, but the
probability is that they are photographed, so to speak, on the eye and
counted afterwards. It is the general belief of psychologists at present
that the mind attends to only one thing at a time, that only one idea or
object can occupy the focal point in consciousness.

The apparent contradiction between ordinary experience and psychological
experience along this line is due to three facts which are often
overlooked. In the first place, the complexity of the idea or thing that
can be attended to as a unit varies tremendously. Differences in people
account for part of this variation, but training and experience account
for still more. Our ideas become more and more complex as experience and