ry area" for the particular sense stimulated.
When the eye is stimulated, the nerve current first reaches a small
portion of the occipital lobe, called the visual sensory area. Without
that area there is no visual sensation. When the ear is stimulated,
the conscious sensation is the response of a small portion of the
temporal lobe called the auditory sensory area, and without this area
there is no auditory sensation. But the presence of the visual sensory
area is not enough to give the visual perception of facts, nor is the
presence of the auditory sensory area enough to give auditory
perception. The cortical regions _adjacent_ to the sensory areas are
necessary for perception; if they are destroyed, the individual may
still see, but not know the objects seen; or may still hear, but not
recognize the words or tunes that he hears. If the cortical area
destroyed is in the parietal {424} lobe, adjacent to the sensory area
for the cutaneous and kinesthetic senses, he may still "feel" objects,
but without being able to distinguish an apple from a lump of coal, or
a folded newspaper from a tin pail.

Sense perception, then, is a response of areas adjacent to the sensory
areas, and this response is aroused by nerve currents coming along
"association fibers" from the sensory areas which are first aroused
from the sense organs.

The whole chain of events, from the time the stimulus reaches the
sense organ to the time the fact is perceived, occupies only a fifth
or even a tenth of a second in simple cases, and the interval between
the beginning of the sensation to the beginning of the perception is
not over a twentieth when the fact is easily perceived. Since the
sensation usually lasts for longer than this, it overlaps the
perception in time, and the two conscious responses are so _blended_
that it is difficult or impossible for introspection to separate them.

But when an unusual fact is presented, perception may lag, though
sensation occurs promptly. We may be baffled and confused for an
instant, and have sensation without any definite perception; or, more
often, we make a rapid series of _trial and error perceptions_. In one
instance, a noise was first heard as distant thunder, and then,
correctly, as somebody walking on the floor above. In another case, a
faint sound was first taken for a bird singing, then for a distant
locomotive whistle, and finally for what it was, the tinny noise of a
piece of metal carried in the ha