of it", and were strongly tempted to accuse them of poor
introspection, if not worse. It is true that in attempting to study
images, we have to depend altogether on introspection, since no one
can objectively observe another person's memory image, and therefore
we are exposed to all the unreliability of the unchecked introspective
method. But at the same time, when you cross-question an individual
whose testimony regarding his imagery is very different from yours,
you find him so consistent in his testimony and so sure he is right,
that you are forced to conclude to a very real difference between him
and yourself. You are forced to conclude that the power of recalling
sensations varies from something like one hundred per cent, down to
practically zero.

Individuals may also differ in the _kind_ of sensation that they can
vividly recall. Some who are poor at recalling visual sensations do
have vivid auditory images, and others who have little of either
visual or auditory imagery call up {370} kinesthetic sensations
without difficulty. When this was first discovered, a very pretty
theory of "imagery types" was built upon it. Any individual, so it was
held, belonged to one or another type: either he was a "visualist",
thinking of everything as it appears to the eyes, or he was an
"audile", thinking of everything according to its sound, or he was a
"motor type", dealing wholly in kinesthetic imagery, or he might, in
rare cases, belong to the olfactory or gustatory or tactile type.

[Illustration: Fig. 54.--Individual differences in mental imagery.
According to the type theory, every individual has a place in one or
another of the distinct groups, visual, auditory, tactile,
kinesthetic, or olfactory. According to the facts, the majority, of
individuals cluster in the middle space, and form a single large
group, though some few are extremely visual, or auditory, etc., in
their imagery. (Figure text: according to the type theory, according to
the facts)]

But the progress of investigation showed, first, that a "mixed type"
must also be admitted, to provide for individuals who easily called up
images of two or more different senses; and, later on, that the mixed
type was the most common. In fact, it is now known to be very unusual
for an individual to be confined to images of a single sense. Nearly
every one gets visual images more easily and frequently than those of
any other sense, but nearly every one has, from time