The experimental method, known also as the method of Mental Tests (q.v.), is usually applied to children of school age. Devised by educators and used by them for purposes of experimental pedagogy, these tests seek to de termine the child's mental ability as shown by his reaction-time, visual and auditory sense perception, power of concentration, the curve of fatigue, etc. The advantages of this method over the other are that it deals with children collectively rather than as individuals, thus fur nishing data of greater scientific value, and that the personal equation of the parental or other doting observer of an individual child is here entirely eliminated. Thus, while the diary method is far more comprehensive, extending as it usually does ever years, the experimental method is generally more scientific. Notable specimens of collective studies of children are Sully's 'Studies of Childhood' and Baldwin's 'Mental Development in the Child and in the Race.' But a sufficiently large number of indi vidual studies, properly analyzed and inter preted, may yield results that are equally re liable. As both methods have their obvious limitations, neither of them is self-sufficient for scientific child study and each should be used to supplement the other.
Another method, which really partakes somewhat of the nature of the two methods already mentioned, is known as the "ques tionnaire method?' This involves reports on the child's behavior made by parents, teachers and others in response to special lists of ques tions prepared for them. In so far as this method depends upon partial and untrained observers, it is open to the same objections as the diary method. The accuracy of the final conclusions reached by this means is often still further impaired by arbitrary classification and interpretation on the part of the question framer, who cannot be aware of the conditions under which the information solicited was ob tained. For these reasons this method, save under exceptionally favorable circumstances, has proved of little scientific value. Few psychologists have ever used it, and fewer still use it at present.
Finally, mention might here be made also of another means— it is in no sense a method —of getting indirect light on the intricate problems of child study. This is a sort of "reminiscent introspection') by which adults, usually authors, attempt to resurrect for us their childhood experiences. The famous autobiographies of Tolstoy, Loti and John Stuart Mill afford such reminiscences. The danger of reading into such recollections ele ments belonging to a later period of develop ment is indeed very great. Even in cases of unquestioned sincerity such reminiscences of childhood are apt to assume the nature of romantic autobiography.
Such other methods as are used in child study are not peculiar to this subject, hut are borrowed from the other sciences — physiology, anthropometry, etc.— dealing with the physical nature of man. These, therefore, need not be described in the present article.
Principles and Results.— The fundamental principle of child study, that the child is not to be considered an adult in miniature, has al ready been referred to. Another essential con sideration which must ever be borne in mind in this connection is that, both physiologically and psychologically, the child is a more dynamic being than the adult. The lattet need but live, whereas the former must lire and grow. The adult's physiological existence is
better co-ordinated and regulated; hence there is greater equilibrium in his case. The child, on the other hand, owing to continuous growth and consequent readjustment, is in a constant state of flux. Hence his restlessness and lack of concentration, which unenlightened teachers and ignorant parents vainly deplore. A third guiding principle in child study is that children vary less among themselves than adults, pre senting a uniformity which increases inversely as their ages. Still another controlling truth is the most significant recognition that play is the child's chief business in life. The old notions that play in the child serves no pur pose other than that of mere recreation, or that it is but an outlet for surplus energy, have long been abandoned. In their stead—and there were many variations of these fallacies the view that play in childhood has a very im portant ulterior end has won universal accept ance. The recognition of the educational and biological significance of play, a direct corol lary of the general theory as to the meaning of infancy, has revolutionized modern child-train ing and education.
The most concrete results of child study have, naturally, been physical or physiological. In these respects the division of the period of childhood into different stages, according to marked lines of development, may he con sidered the most important step. While there is still no complete agreement among writers on child study as to the exact years marking the boundaries, these three periods may be ac cepted as approximately correct: (1) Infancy, the first six years — about a year less for girls; (2) Childhood, the 7th to the 12th year — about two years less for girls; and (3) Adolescence, from the close of childhood to about the 25th year—about the 21st for girls. The impossi bility of establishing very exact boundaries here is due to numerous variations from the normal stages of physical development. Such individual differences may result from various causes — prenatal tendencies and environ mental influences — and must always be reckoned with in making general deductions from child study. In spite of these difficulties, however, it has been determined that all nor mal children grow very rapidly during the first five years, at a slower rate from 5 to 12, faster again till about the 14-15th year, and at a rapidly decreasing rate thereafter till the age of maturity. But even these generalizations must be qualified by the statement that the rates of growth here indicated do not neces sarily imply parallel or uniform development in height and weight or for all parts of the body. For a child of seven may happen to have the •weight of an eight-year-old and the height of one who is but six. Nor should the essential differences between the growth of boys and girls ever be lost sight of. For in stance, the rate of growth before the close of the prepubertal period is faster for girls than for boys, making the former heavier than the latter. Again, girls attain the normal height of adulthood at the age of 18, while boys arc not full-grown men before the 20th or 21st year. Sexually, too, girls mature considerably earlier than boys, passing through the period of adolescence (q.v.) about four years sooner, as already indicated.