elatively simple--that is, before the nervous system has grown to
maturity. For example, psychology used to hold that we have a "speech
faculty," an inborn mental endowment which is incapable of further
analysis; but support for the position is wanting when we turn to the
brain of the infant. Not only do we fail to find the series of centres
now known to be the "speech zone," but even those of them which we do
find have not yet taken up this function, either alone or together. In
other words, the primary object of each of the various centres
involved is not speech, but some other and simpler function; and
speech arises by development from a union of these separate functions.

4. In observing young children, a more direct application of
experiment is possible. By "experiment" here I mean both experiment
on the senses and also experiment directly on consciousness by
suggestion, social influence, etc. In experimenting on adults, great
difficulties arise through the fact that reactions--such as performing
a voluntary movement when a signal is heard, etc.--are complicated by
deliberation, habit, custom, choice, etc. The subject hears a sound,
identifies it, and presses a button--_if he choose_ and agree to do
so. What goes on in this interval between the advent of the incoming
nerve process and the discharge of the outgoing nerve process?
Something, at any rate, which represents a brain process of great
complexity. Now, anything that fixes or simplifies the brain process,
in so far gives greater certainty to the results. For this reason
experiments on reflex actions are valuable and decisive where similar
experiments on voluntary actions are uncertain and of doubtful value.
Now the child's mind is relatively simple, and so offers a field for
more fruitful experiment; this is seen in the reactions of the infant
to strong stimuli, such as bright colours, etc., as related further
on.

With this inadequate review of the advantages of infant psychology, it
is well also to point out the dangers of the abuse of it. Such dangers
are real. The very simplicity which seems to characterize the life of
the child is often extremely misleading, and this because the
simplicity in question is sometimes ambiguous. Two actions of the
child may appear equally simple; but one may be an adaptive action,
learned with great pains and really very complex, while the other may
be inadaptive and really simple. Children differ under the law of
heredit