the filled space as his finger was drawn over it. In order to do this,
I held a piece of fine wire across the line of the filled space, and
after the subject had measured off the equal open space he was asked
to tell whether or not he had crossed the wire. The wire was so fine
that considerable attention was necessary to detect it. In some of the
experiments the wire was inserted early in the filled space, and in
some near the end. When it was put in near the beginning, it was
interesting to notice, as illustrating the amount of attention that
was being given to the effort of finding the wire, that the subject,
as soon as he had discovered it, would increase his speed, relax the
attention, and continue the rest of the journey more easily.

The general effect of this forcing of the attention was to increase
the apparent length of the filled space. This conclusion was reached
by comparing these results with those in which there was no compelled
attention. When the obstacle was inserted early, the space was judged
shorter than when it came at the end of the filled space. This shows
very plainly the effect of continued concentration of attention, when
that attention is directed intensely to the spot immediately under the
finger-tip. When the attention was focalized in this way, the subject
lost sight of the space as a whole. It rapidly faded out of memory
behind the moving finger-tip. But when this concentration of attention
was not required, the subject was able to hold together in
consciousness the entire collection of discrete points, and he
overestimated the space occupied by them. It must be remembered here
that I mean that the filled space with the focalized attention was
judged shorter than the filled space without such concentration of
attention, but both of these spaces were judged shorter than the
adjacent open space. This latter fact I shall attempt to explain
later. Many other simple devices were employed to oblige the subject