The Source of Native Traits
"Native" means a little more than "congenital." A child may be born blind, having been infected by disease germs shortly before birth; he may be congenitally an idiot because of head injury during a difficult birth; or his mentality may have been impaired, during his uterine life, by [{91}] alcohol reaching his brain from a drunken mother. Such traits are congenital, but acquired. Native traits date back to the original constitution of the child, which was fully determined at the time when his individual life began, nine months before birth. The "fertilized ovum", formed by the combination of two cells, one from each of the parents, though microscopic in size and a simple sphere in shape, somehow contains the determiners for all the native or inherited traits of the new individual.
It is very mysterious, certainly. This microscopic, featureless creature is already a human individual, with certain of its future traits--those that we call "native"--already settled. It is a human being as distinguished from any other species, it is a white or colored individual, male or female, blonde or brunette, short or tall, stocky or slender, mentally gifted or deficient, perhaps a "born" musician or adventurer or leader of men. These and all other native traits are already determined and latent within it; and the only question, regarding such traits, is whether the environment is going to be such as to enable this young individual to live and mature and unfold what is latent within it.
Reactions Appearing at Birth Must Be Native
For the first few months of the individual's existence, sheltered as it is within the mother's body, there is no chance for any acquisition, except of certain abnormalities such as were alluded to above. What occurs during this prenatal period is natural development, not learning or any effect of experience. The traits displayed by the new-born child are, accordingly, native traits. His breathing, crying, starting at a noise, squirming, stretching, grasping, sucking and swallowing, and other movements made from birth on, are to be counted as native reactions, that is to say, as [{92}] reactions executed by sensory, muscular and nervous machinery that have become ready for use by the mere process of natural growth. This is the first and clearest sign of a native trait, that it shall appear at birth.
Reactions That Cannot Be Learned Must Be Native
But native traits continue to make their appearance as the child's development proceeds after birth. Inherited anatomical traits, like stature and build, hair color, beard, and shape of nose, though certainly determined by native constitution, do not fully make their appearance till maturity. In fact, what does maturity mean, except that the natural characteristics have finally reached their complete development? And it is as true of internal structure as of external, that natural development, far from being complete at birth, keeps on till maturity. The neurones continue to grow, and their synapses in the nerve centers to become closer knit, just by virtue of natural growth; and thus reflex arcs, and other reaction machinery, one by one reach the ready-to-use stage during the individual's growing-up, especially during the first few years. With the growth to a functional condition of their sensori-neuro-muscular mechanisms, mental and motor reactions that are native, though not present at birth, make their appearance. The native intelligence of the child gradually unfolds, likewise his special native "gifts" and his inherited emotional and impulsive traits.
Of course it is more difficult to make sure that a trait is native when it does not appear till some time after birth, for the chance of acquiring it by a process of learning has to be taken into account. If you can so control the conditions under which the young individual grows as to eliminate the possibility of learning a certain act, then you can [{93}] make sure whether the act is acquired or provided by the native constitution.
Experimental Detection of Native Reactions
Take the question whether birds learn to fly or simply come to fly when their natural development has gone far enough. The newly hatched bird cannot fly; its muscles are not strong enough, its wings are not feathered, and its nerve mechanism for coördinating the wing movements has still some growth to make before being ready for use. But, under ordinary conditions, the young bird has some chance to learn flying, by watching the old birds fly and by trying and gradually getting the motion. The old birds, after a time, push the young ones from the nest and seem, to our eyes, to be teaching them to fly. Experiment enables us to decide the question. One of the earliest experiments in animal psychology was made by Spalding in 1873. He took newly hatched birds from the nest and shut each one separately in a little box that gave it no chance to stretch its wings or to see other birds fly. Here he fed and cared for them till the age at which flying usually begins, and then released them. Off they flew, skilfully managing wings and tail, swooping around the trees and soon disappearing from sight. A very successful experiment!--and conclusive. The little birds had had no chance to learn to fly, yet they flew. Flying must have come to them in the natural course of growth.