movement suggested by an idea had been treated as if equivalent
to the movement actually made by the eye in following a long
line; the intrinsic interest--that is, the ideal interest--of
an object insignificant in form was equated to the attractive
power of a perspective, which has, presumably, a merely
physiological effect on the visual mechanism.

I believe, however, that the justification of this apparent
heterogeneity, and the basis for explanation, is given in the
reduction of all elements to their lowest term,--as objects
for the expenditure of attention. A large object and an
"interesting" object are "heavy" for the same reason, because
they call out the attention. And expenditure of effort is
expenditure of attention; thus, if an object on the outskirts
of the field of vision requires a wide sweep of the eye to take
it in, it demands the expenditure of attention, and so is felt
as "heavy." But what is "the expenditure of attention" in
physiological terms? It is nothing more than the measure of
the motor impulses directed to the object of attention. And
whether the motor impulse appears as the tendency to follow
out the suggestions of motion in the object, all reduces to
the same physiological basis.

It may here be objected that our motor impulses are, nevertheless,
still heterogeneous, inasmuch as some are toward the object of
interest, and some along the line of movement. But it must be
said, first, that these are not felt in the body, but transferred
as values of weight to points in the picture,--it is the amount
and not the direction of excitement that is counted; and secondly,
that even if it were not so, the suggested movement along a line