the fact that the
notes are uneven in length, and meanwhile using his feet on the
pedals, what has he got left to beat time with? No one has located the
stimulus to which accurate time perception responds, though, in a
general way, we are pretty sure that change of one sort or another is
the datum. With longer intervals, from a minute to several hours, the
sign of duration is probably the amount happening in the interval, or
else such progressive bodily changes as hunger and fatigue.

The Perception of Space

Stimuli for the perception of location are provided by all the senses.
We perceive a taste as in the mouth, thirst as in the throat, hunger
pangs as in the stomach. To a familiar odor we may respond by knowing
the odorous substance to be close at hand. To stimulation of the
semi-circular canals we respond by knowing the direction in which we
are being turned.

We respond to sounds by knowing the direction from which they come,
and the distance from which they come; {440} but it must be confessed
that we are liable to gross errors here. To perceive the distance of
the sounding body we have to be familiar with the sound at various
distances, and our perception of distance is based on this knowledge.
As to the direction of sound, experiment has proved that we do little
more than distinguish between right and left; we are all at sea in
attempting to distinguish front from back or up from down. Apparently
the only datum we have to go by is the different stimulation given the
two ears according as the sound comes from the right or left.

The remaining senses, the cutaneous, the kinesthetic and the visual,
afford much fuller data for the perception of spatial facts. Movements
of the limbs are perceived quite accurately as to direction and
extent.

A cutaneous stimulus is located with fair exactness, though much less
exactly on such regions as the back than on the hands or lips. If you
were asked how you distinguished one point from another on the back of
the hand, you could only answer that they felt different; and if you
were further asked whether a pencil point applied to the two points of
the skin did not feel the same, you would have to acknowledge that it
did feel the same, except that it was felt in a different place. In
other words, you would not be able to identify the exact data on which
your perception of cutaneous position is based. Science has done no
better, but has simply given the name of "local sig