Language is primarily an auditory system of symbols. In so far as it is
articulated it is also a motor system, but the motor aspect of speech is
clearly secondary to the auditory. In normal individuals the impulse to
speech first takes effect in the sphere of auditory imagery and is then
transmitted to the motor nerves that control the organs of speech. The
motor processes and the accompanying motor feelings are not, however,
the end, the final resting point. They are merely a means and a control
leading to auditory perception in both speaker and hearer.
Communication, which is the very object of speech, is successfully
effected only when the hearer's auditory perceptions are translated into
the appropriate and intended flow of imagery or thought or both
combined. Hence the cycle of speech, in so far as we may look upon it as
a purely external instrument, begins and ends in the realm of sounds.
The concordance between the initial auditory imagery and the final
auditory perceptions is the social seal or warrant of the successful
issue of the process. As we have already seen, the typical course of
this process may undergo endless modifications or transfers into
equivalent systems without thereby losing its essential formal
characteristics.

The most important of these modifications is the abbreviation of the
speech process involved in thinking. This has doubtless many forms,
according to the structural or functional peculiarities of the
individual mind. The least modified form is that known as "talking to
one's self" or "thinking aloud." Here the speaker and the hearer are
identified in a single person, who may be said to communicate with
himself. More significant is the still further abbreviated form in which
the sounds of speech are not articulated at all. To this belong all the
varieties of silent speech and of normal thinking. The auditory centers
alone may be excited; or the impulse to linguistic expression may be