judging the intelligence of people with whom we associate every day, we
regard one who is able to maintain close attention for long periods of
time as a person of strong mind. We rate Thomas Edison as a powerful
thinker when we read that he becomes so absorbed in work that he
neither eats nor sleeps. Finally, when we examine the insane and the
feeble-minded, we find that one form which their derangements take is
an inability to control the attention. This evidence, added to our own
experience, shows us the importance of concentration of attention in
study and we become even more desirous of investigating attention to
see how we may develop it.

We shall be better able to discuss attention if we select for analysis
a concrete situation when the mind is in a state of concentrated
attention. Concentrate for a moment upon the letter O. Although you are
ostensibly focussing all your powers of attention upon the letter,
nevertheless you are really aware of a number of things besides: of
other words on the page; of other objects in the field of vision; of
sounds in the room and on the street; of sensations from your clothing;
and of sensations from your bodily organs, such as the heart and lungs.
In addition to these sensations, you will find, if you introspect
carefully enough, that your mind also contains a number of ideas and
imaginings; thoughts about the paragraph you just read or about one of
your lessons. Thus we see that at a time when we apparently focus our
attention upon but one thing, we really have a large number of things
in our mind, and they are of a great variety. The mental field might be
represented by a circle, at the centre of which is the object of
attention. It may be an object in the external world perceived through
one of the senses, or it may be an idea we are thinking about, such,
for example, as the idea of infinity. But whether the thing attended to
is a perception or an idea, we may properly speak of it as the object
of attention or the "focal" object. In addition to this, we must
recognize the presence of a large number of other objects, both sensory
and ideational. These are nearer the margin of the mental field, so we
call them "marginal."

The distinctive thing about a state of mind such as that just described
is that the focal object is much clearer than the marginal objects. For
example, when you fixated the letter O, it was only in the vaguest sort
of fashion that you were aware of the co