While it is universally recognized that no two individuals are exactly alike, we are not at all clear in our minds as to whether the important differences arise from differences in experience or nurture, or from essential differences in nature. We know that children of the same parents are essentially different from birth, and that no matter how similar the treatment they receive afterward they will always remain different, or even become more different as they become older. It is becoming more clear every day, as a result of scientific study, that every individual is absolutely unique, excepting only "true" twins.
If we accept this individuality of the person as a fact, what, then, is the importance of training or environment? Does not this admission settle at once the contention of those who see no value at all in a carefully-controlled environment? If this child is born without mathematical ability, what is the use of drumming arithmetic into his head; or, if he is born with musical genius, why should we bother about teaching him music?—he will "take" to it naturally.
The answer to these and similar questions is to be found in the answer to another question, namely, "What is it precisely that the child is born with?" Surely no child is ever born with the ability to dance or sing or to do sums in algebra. When we say that a child has musical genius we mean merely that as he develops we may notice in him a certain capacity to acquire musical knowledge more readily than most other children do, or a certain disposition to express himself in melody, or a certain liking for music in some form, or a certain readiness to acquire control of musical instruments. In other words, the child is born with a capacity for acquiring certain things, from the outside, that is, from the environment—he is born with certain possibilities, which can become actualities only if the suitable conditions are provided. In the same way one child is born with a capacity for exceptional muscular development, and another for exceptional self-mastery. But in every case practice makes perfect, the muscles must be properly nourished and exercised, the will must be trained—and that means suitable environment.
Now, while every individual is unique, not every child is a born genius. The distinctiveness of each child lies in the fact that he consists of a combination of capacities and tendencies, each of which varies in degree when compared with other individuals. For example, Evelyn has about the same capacity for physical work as Annie, but she stands lower than the latter in arithmetic and higher in language work. John shows about the same physical power as Henry, when measured by running and jumping and chinning; but John can hit the ball with his bat more times out of a hundred than Henry can, whereas Henry can hit the bull's-eye with his rifle more times out of a hundred than John can. In a thousand details any two children differ from each other, one excelling in nearly half of the points, the other excelling perhaps in about as many, and the two standing almost exactly alike in some matters.
A child that excels most of his colleagues in one or a few points is said to have marked ability in that direction—as the exceptional athlete, or the child with exceptional literary or moral feeling. On the other hand, a child that seems to measure well up to the average in most points, and even to excel in a few, may fall far short in some matters,—that is, may be deficient. Thus a perfectly good child in every other way may be unable to master the ordinary requirements in arithmetic, or a child may have an entirely satisfactory development in every way and be deficient in musical discrimination.
Another kind of difference is to be found in what may be called general capacity. Some children show higher capacity than the average along nearly every line that can be measured or tested, without showing a preponderance in any one direction. Such children are said to be of high grade, or of high "vitality." In the same way many children are below the average in nearly every line, without being particularly defective along any one line. They can do one thing about as well as another, just as the high-grade boys and girls can do one thing about as well as another; but in the former there is a limit to the possible development which is exceeded in the latter. Among both classes of children the full development depends upon suitable environment, but what is suitable for one may not be suitable for the other.
From a consideration of these differences in degree and difference in kind we may see that there is no course of training or treatment, no method of instruction, no trick for the mother or for the teacher that will be usable for all children under all circumstances, to make them all come up to some preconceived uniform standard. On the other hand, if we consider the differences as worth developing, and even emphasizing, it must be obvious that the training and the treatment should be adapted to the individual child so far as possible. Starting out with essentially different human beings, uniform treatment will not make them all alike, nor will any treatment make them all alike. But starting out with a particular human being, we can learn to treat him in such a way as to make him develop into a more desirable person than he would become if he were neglected or if he were treated differently. And that is the main problem, after all.
The relation between heredity and environment may perhaps be made clear by an extreme illustration from the physical side. Here are two full-grown men, both five feet and four inches tall. We observe that they are both short. Now, the shortness of one of them turns out to be the result of heredity,—that is, he belongs to a strain of short people. No amount of feeding or of exercise or of special régime could have made him more than a quarter or half an inch taller. The other man, however, belongs to a race of rather taller men and women: his shortness of stature may be traced to undernutrition, or to overwork, or to sickness during his childhood. It is quite certain that a different kind of environment would have resulted in his being as tall as his brothers and sisters.
Now, the problem of training concerns itself practically not so much with the person who is particularly "long" by nature, nor so much with the person who is unusually "short" by nature—and we may apply "long" and "short" to every other trait as well as to stature. The problem with these extremes is simply to keep the child in good health. The special efforts of the teacher and of the parent are devoted to giving the child who appears somewhat below the average in some particular those special stimulations and exercises and feedings that will bring him up to the average. We find the extremely short too discouraging, and the extremely long do not clamor for our attention; but it is those near the middle-point that we want to help over to the other side of the dividing line. And this is just as true of an undesirable character as it is of a desirable one. We take no trouble to teach honesty to the child that seems instinctively honest; and we give up in despair with the child that convinces us of his utter lack of a moral sense: we concentrate our efforts upon the delinquents whom we catch early, or upon those who are in danger of sliding down if they are not helped along.
Perhaps one reason for the great confusion on this subject arises out of the fact that we have become accustomed to making a sharp distinction between physical characters on the one hand and so-called mental and moral qualities on the other. Every one recognizes family resemblances in physical features. A particular shape of nose or a peculiarity of the hand appears in every member of the family, sometimes for several successive generations. Facts like these we accept as evidence of "heredity" without any question. We also recognize that the Joneses of Centerville always take the measles "hard," whereas with the Andersons vaccination never "takes." But when it comes to mental qualities, which we are not accustomed to measure or to recognize with the same degree of discrimination, most of us fail to see that heredity is just as common for these as for physical traits. Moreover, mental qualities take on such a great variety of forms that their recognition is made doubly difficult. Thus it may be the same mental traits that make of a certain man a successful lawyer, of his brother an able scientist, and of their cousin a clever criminal. No doubt each of these three men has qualities in a degree lacking in the others; but the point is that they have many qualities in common which are obscured by the different lines of development they have followed.