2.
The specific adaptability of an immature creature for growth constitutes
his plasticity. This is something quite different from the
plasticity of putty or wax. It is not a capacity to take on change of
form in accord with external pressure. It lies near the pliable
elasticity by which some persons take on the color of their surroundings
while retaining their own bent. But it is something deeper than this.
It is essentially the ability to learn from experience; the power to
retain from one experience something which is of avail in coping with
the difficulties of a later situation. This means power to modify
actions on the basis of the results of prior experiences, the power to
develop dispositions. Without it, the acquisition of habits is
impossible.
It is a familiar fact that the young of the higher animals, and especially
the human young, have to learn to utilize their instinctive reactions.
The human being is born with a greater number of instinctive tendencies than
other animals. But the instincts of the lower animals perfect themselves
for appropriate action at an early period after birth, while most of those
of the human infant are of little account just as they stand. An original
specialized power of adjustment secures immediate efficiency, but, like a
railway ticket, it is good for one route only. A being who, in order to use
his eyes, ears, hands, and legs, has to experiment in making varied combinations
of their reactions, achieves a control that is flexible and varied. A
chick, for example, pecks accurately at a bit of food in a few hours
after hatching. This means that definite coordinations of activities of
the eyes in seeing and of the body and head in striking are perfected in
a few trials. An infant requires about six months to be able to gauge
with approximate accuracy the action in reaching which will coordinate
with his visual activities; to be able, that is, to tell whether he can
reach a seen object and just how to execute the reaching. As a result,
the chick is limited by the relative perfection of its original
endowment. The infant has the advantage of the multitude of instinctive
tentative reactions and of the experiences that accompany them, even
though he is at a temporary disadvantage because they cross one another.
In learning an action, instead of having it given ready-made, one of
necessity learns to vary its factors, to make varied combinations of
them, according to change of circumstances. A possibility of continuing
progress is opened up by the fact that in learning one act, methods are
developed good for use in other situations. Still more important is the
fact that the human being acquires a habit of learning. He learns to
learn.
The importance for human life of the two facts of dependence and
variable control has been summed up in the doctrine of the significance
of prolonged infancy.
[1]
This prolongation is significant from the standpoint
of the adult members of the group as well as from that of the young.
The presence of dependent and learning beings is a stimulus to nurture
and affection. The need for constant continued care was probably a
chief means in transforming temporary cohabitations into permanent
unions. It certainly was a chief influence in forming habits of
affectionate and sympathetic watchfulness; that constructive interest in
the well-being of others which is essential to associated life.
Intellectually, this moral development meant the introduction of many
new objects of attention; it stimulated foresight and planning for the
future. Thus there is a reciprocal influence. Increasing complexity of
social life requires a longer period of infancy in which to acquire the
needed powers; this prolongation of dependence means prolongation of
plasticity, or power of acquiring variable and novel modes of control.
Hence it provides a further push to social progress.
