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So far as convenience goes this is very satisfactory; but the question of “mental age," does not need to be dismissed in quite so summary a fashion. It is not necessary in seeking to avoid over exactness of statement to throw away so completely the consideration of measurable mental performances belonging to given periods of growth and development. Certain performances, mental and physical, may be expected to appear at certain times in the history of the individual. The fact that these stock performances may appear before or after the expected period does not alter the general fact; it simply raises the questions of when and why, often leading to very valuable results for the understanding of individual cases. It is of very great advantage to know what mental performances are characteristic of certain growth periods, and also to know how exactly the appearance of the growth changes that accompany the coming and going of the different growth periods can be stated in terms of years and months. Indeed, it is quite possible that the use of “Age Scales” may come to be confined pretty much to this task, of recording the progress of individuals through the mental development of a given growth period, instead of the present very questionable effort of tallying off mental performances with single years. As a matter of fact, as every user of the Binet and Simon Age Scale knows, this is exactly what Binet did when he had passed the Ten-Year level of his scale, the tests after that representing periods rather than years. The most serious confusion arising from Goddard's treatment of the Binet Scale was the introduction of additional tests and the arrangement of the old tests in such a way as to obscure the progress of Binet's development of his scale away from year tests toward growth period tests.

Considerable light has been thrown on the matter of growth periods and their characteristic mental behavior by Prof. F. Boas of Columbia University, and Dr. C. Ward Crampton, Director of Physical Training of the Department of Education, New York City, and certainly all the users of the Binet and Simon Scale in this locality ought not to overlook the great significance of their conception of “physiological age”' in its bearing on the interpretation of mental tests. The general principle appears in Boas' statement that “during school age the individual differences may be measured by a probable variation of about 2. ' years. These data refer only to the development of certain organs; but thy are an indication of the variability of the development of the whole body, although nervous, muscular, osseous, etc., systems may each develop somewhat independently of each other. The measurements of children of the same age represent, therefore, individuals of different physiological developments; and these differences are the greater, the older the children.... During this term [school age] the individual differences i nmeasurement, structural and functional traits, must be the greater, the more rapid the rate of development and growth."

Crampton's conception of physiological age "affirms the fact that mental and physical development of children, adolescents, and adults, proceeds through

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easily cognizable stages, and maintains that all classification and grouping of the growing and developing human being should take cognizance of and relate themselves primarily to these stages; and, secondarily, and in a decidedly minor way, to the artificial groupings upon the basis of the school grade or chronological age.'

"This doctrine is based upon a careful but as yet incomplete survey of developmental stages, and a search for easily recognizable signs which accompany each stage. The developmental signs may be anatomical, such as the appearance of the six-year molar, the wisdom tooth, the public hair; physiological, such as menstruation, change of voice, menopause; or psychological, such as change of rote to associative memory, the wane of the collecting tendency, the budding of the earning instinct; and, later, the characteristic rumination of senescence.

“In short, we have sought to ascertain by extended and intensive investigation what the significant stages of change may be, and to discover easily recognizable signs whereby we may, from observation, denominate a child or adult to be in this or that stage, so that we may place him in classes of individuals of the same stage of development for the purpose of adjusting and standardizing our medical, scholastic and social treatment to natural instead of artificial requirements."

"Intra-uterine growth is extremely rapid; after birth, it is followed by a rapidly decreasing rate of growth and development, until, at the age of 2 or 3, the child begins to grow at a slowly increasing rate, until a plateau of almost no growth and development is reached at about the chronological age of 7 or 8. The static condition is maintained until there has commenced the great pubertal age. At this time, the most important epoch of adult life, second only in significance to the event of birth, the child commences a period which can only be likened to an explosion of growth and development. He begins to grow tall with great rapidity; weight is added pound by pound, and, with the increased bulk, comes a rapid addition to the muscle, strength and motor ability. This age is most prone to begin during the warm months of the summer, and when it does occur, a single month may add an inch in height, 20 pounds in weight, and double the muscle force. After a variable length of time, a year, or a year and a half, the increase in height, weight and strength gradually return to a slower rate, and the body and mind proceed with a stage of ripening which we call adoles

* * In this catalogue of events, physiological and mental growth do not proceed in an orderly fashion year by year. Some may be hurried, others retarded. Individuals rush past others for a time, and then lag behind We cannot tell, from the number of years which the individual has lived what stage of development he may be in.

The calendar and the chronological age based upon it do not give us trustworthy information, and, strange to contemplate, the general error of science, medicine and education is a blind adherence to a chronological age.”

Boas and Crampton have both worked out with some exactness the variable limits of these growth periods in the developing life of the human individual. Following their criteria it is possible to note during school life the three main growth periods of pre-pubescence, pubescence and post-pubescence. Or, if we use certain other equally familiar terms, we may designate these periods as later childhood, pre-adolescence and early adolesence. Crampton's dates for the

cence.

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upper and lower limits of each of these periods were obtained by the examination of 3,835 boys of high school age in New York City, 98 per cent. of whose parents were American born. It will be seen at once that expectations based on the examination of such a group will vary in numerous ways from the facts observed in groups made up in the quite different way common in the experience : of most Ungraded class teachers. Still this does not materially alter the main significance of his figures. These show that the group between 12 and 12.5 years, or, roughly speaking, the 12 year group, contained 81 per cent. who were still in later childhood. The proportion for each half year is given in his tables. By 15 years only 9 per cent. have failed to pass beyond the later childhood stage. By 17 years practically all have passed beyond this stage.

The period of pubescence or the pre-adolescent period is briefer, and boys move into and out of it so quickly that in the 2, or at most, 3 years chiefly devoted to these changes the proportion of the pre-adolescent group to the whole group of high school age is always low. At 12 years 6 per cent. are in this period. At 13 years 26 per cent. are found here. This proportion is well maintained up to 15 years when the proportion falls to 20 per cent. and is then rapidly reduced, until by 17 years practically all have passed through these two periods that immediately precede early adolescence. To quote Crampton: “It appears from this table that there are six half years, from 12.5 to 15.5, in which there are 20 per cent, or more of the population who are in the stage of pubescence. In no one half year is the per cent. of pubescents over 30 per cent. Therefore it is not fair to give to any one year the designation, 'the year of pubescence,' for at any age the large majority are not pubescents.” The term “pubescent," in other words, is correctly used of a period, not of any year, and this period covers at the most about 2 years of life, beginning anywhere from 12 to 15 years and running on to anywhere from 15 to 18 years, to be determined in any given case by certain anatomical, physiological and mental signs.

The post-pubescent or early adolescent period is much the longer of the three. At 13 years 18 per cent. of the group are in this period; at 14 years 46 per cent. are found here; at 17 years 98 per cent. are in this early adolescent stage. The obvious thing to do, for anyone who wishes to use and interpret the Binet and Simon age scale scientifically, is to acquire a working familiarity with the small number of physical signs necessary to identify the exact period of development, and to apply it in every case that comes up. This makes it possible for the student of "mental age" and "physiological age” to find out how long the subject has been established in a given growth period, and how he has fared in his attempts to establish himself in the habitual use of the abilities that belong to the period. There are some difficulties that will occur to every examiner in the way of getting exact information about progress through one of the growth periods, but in practice it is usually quite worth an elaborate effort to get even approximate data. It is just here that the Ungraded class teacher, and the school visitor, and the clinical psychologist are obliged to make their

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own modifications of the age expectations based upon the study of Boas's and Crampton's tables. It may be true that by 14 to 14.5 years 46 per cent. of the children in a picked group are adolescent. But it does not follow that all of this 46 per cent, have taken on the habitual behavior of adolescents. There is always need to reckon with the influence of the others of this age who are not yet adolescent, and who have a conservative influence over habit formation not always recognized. There will be again the powerful influence of those of the same age who are adolescent, but of an inferior type of development. There are also strong limitations to development proceeding from racial, social and economic conditions, which slow down the rate of appearance of characteristic forms of behavior. Last, and not least important of all, there is the question of the effect of accidental causes such as diseases, like chorea, habit spasms, anemia, especially in adolescent girls, or any of the familiar list of pre-adult diseases. These considerations are of increasing importance as the growth periods progress, and noticeably so in the early adolescent and later adolescent periods, when profound nervous disorders begin to appear, such as tend to neurasthenia, hysteria or depression. In other words, the conception of “mental age” is a more indefinite one than is recognized by ordinary interpreters of the Binet and Simon scale; and the conception of “physiological age” is a more plastic one than is some times reckoned with by the interpreters of growth period changes. Dr. G. Stanley Hall, for example, seems to have failed to give us the maximum of help in this particular, by diverting attention too strongly toward a theoretical average age for these periods.

In the work of mental testing carried on at the Neurological Institute, where a fair number of children appear who are of the type usually assigned to Ungraded classes, it has been found convenient to take same such working positions as the following:

1. Both “mental age” and “physiological age” are to be regarded from the point of view of physical growth periods, rather than in the more precise terms of months and years.

2. A growth period can be approximately determined in terms of years and months, within rather wide but well defined limits of variability, but these are always to be checked up by a reference to certain physical signs.

3. For purposes of mental estimating the upper limits of a growth period, stated in years and months, must be set considerably farther ahead for this poorly favored group than for the select group from which figures in current use are taken. Due allowance can thus be made more easily for the full establishment of the mental habits of a period, in the face of the highly prevalent accidents of environment, disease and inheritance.

4. The most usable age limits have been found to be these:

Early childhood, 5 to 8 years. Later childhood, 9 to 11 years. Pre-adolesence, 12 to 14 years. Early adolesence, 15 to 18 years. Later adolesence, 19 to 28 years.

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5. In practice we have found the Binet and Simon tests most characteristic of the later childhood period to be the 7 year tests; of the pre-adolescent period to be the 9 year tests; and of the early adolescent period to be the 10 year tests. To be fully established in one of these periods the subjects must pass all of the tests assigned to it.

8. A specimen interpretation of a Binet and Simon test from this point of view reads as follows:

Chronological age, 15 years, 9 months, 10 days. Binet and Simon score, 8.4. Highest complete Binet and Simon level, 6. Physical growth period, early adolescence. Mental growth period, early childhood. Retardation, three growth periods. Subject co-operated willingly, but has a history of frequent epileptic attacks in early childhood. Such a subject is a highly probable candidate for an ungraded class.

FREDERICK W. ELLIS,
Director of Social Research, The Neurological Institute of New York.

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