much-used neural paths, while new tricks require the connecting up of groups of
neurones not in the habit of working together; and the flow of nerve energy is
more easily accomplished in the neurones accustomed to working together. One
who learns to speak a foreign language late in life never attains the facility and
ease that might have been reached at an earlier age. This is because the neural
paths for speech are already set for his mother-tongue, and, with the lessened
plasticity of age, the new paths are hard to establish.
The connections between the various brain areas, or groups of neurones, are, as
we have seen in an earlier chapter, accomplished by means of association fibers.
This function requires millions of neurones, which unite every part of the cortex
with every other part, thus making it possible for a neural activity going on in
any particular center to extend to any other center whatsoever. In the relatively
unripe brain of the child, the association fibers have not yet set up most of their
connections. The age at which memory begins is determined chiefly by the
development of a sufficient number of association fibers to bring about recall.
The more complex reasoning, which requires many different associative
connections, is impossible prior to the existence of adequate neural development.
It is this fact that makes it futile to attempt to teach young children the more
complicated processes of arithmetic, grammar, or other subjects. They are not
yet equipped with the requisite brain machinery to grasp the necessary
associations.
FIG. 18.—Diagrammatic scheme of association, in which V stands for the visual, A for the
auditory, G for the gustatory, M for the motor, and T for the thought and feeling centers of the
cortex.Association the Basis of Memory.—Without the machinery and processes of