underestimated in comparison with open two-point distances. Fechner[8]
also reported that a line drawn on the skin is judged shorter than the
distance between two points which are merely touched. It will be
noticed, however, that my experiments differed from those of Vierordt
and Fechner in one essential respect. This difference, I think, is
sufficient to explain the different results. In my experiments the
two-point distance was held on the skin, while the stylus was moved
from one point to the other. In their experiments the line was drawn
without the points. This of course changes the objective conditions.
In simply drawing a line on the skin the subject rapidly loses sight
of the starting point of the movement. It follows, as it were, the
moving point, and hence the entire distance is underestimated. I made
a small number of tests of this kind, and found that the line seemed
shorter than the point distance as Fechner and Vierordt declared. But
when the point distance is kept on the skin while the stylus is being
drawn, the filling is allowed its full effect in the judgment,
inasmuch as the end points are perceived as stationary landmarks. The
subjects at first found some difficulty in withholding their judgments
until the movement was completed. Some subjects declared that they
frequently made a preliminary judgment before the filling was
inserted, but that when the moving point approached the end point,
they had distinctly the experience that the distance was widening. In
these experiments I used five sorts of motion, quick and heavy, quick
and light, slow and heavy, slow and light, and interrupted. I made no
attempt to determine either the exact amount of pressure or the exact
rate. I aimed simply at securing pronounced extremes. The slow rate
was approximately 3, and the fast approximately 15 cm. per second.

[7] 'Zeitsinn,' Tübingen, 1858.