Part 7 (1/2)
An extended account of the 1000 tests on which the Stanford revision is chiefly based has been presented in a separate raph This chapter will include only the briefest suation which contribute to the intelligent use of the revision
THE DISTRIBUTION OF INTELLIGENCE The question as to the reat practical as well as theoretical importance One of the most vital questions which can be asked by any nation of any age is the following: ”How high is the average level of intelligence arades of ability above and below the average?” With the develop, for the first time in history, a possible answer to this question
Most of the earlier Binet studies, however, have thrown little light on the distribution of intelligence because of their failure to avoid the influence of accidental selection in choosing subjects for testing Thesubjects for the Stanford revision [19] It is believed that the subjects used for this investigation were as nearly representative of average American-born children as it is possible to secure
[19] See p 52 _ff_ for method used to avoid accidental selection of subjects for the Stanford investigation
The intelligence quotients for these 1000 unselected children were calculated, and their distribution was plotted for the ages separately
The distribution was found fairly sye is on either side of 90 as a median, and at 16 on either side of 80 as a median That the 15- and 16-year-olds test low is due to the fact that these children are left-over retardates and are below average in intelligence
[Illustration: FIG 2 DISTRIBUTION OF I Q'S OF 905 UNSELECTED CHILDREN 5-14 YEARS OF AGE]
The I Q's were then grouped in ranges of ten In the roups including in order the I Q's froly with the descending groups Figure 2 shows the distribution found by this grouping for the 905 children of ages 5 to 14 combined The subjects above 14 are not included in this curve because they are left-overs and not representative of their ages
The distribution for the ages combined is seen to be rees was hardly lessthat only 80 to 120 children were tested at each age In fact, the range, including the middle 50 per cent of I Q's, was found practically constant from 5 to 14 years The tendency is for the middle 50 per cent to fall (approximately) between 93 and 108
Three important conclusions are justified by the above facts:--
1 Since the frequency of the various grades of intelligence decreases _gradually_ and at no point abruptly on each side of theline between norenius Psychologically, theto a distinct type, nor does the genius There is no line of demarcation between either of these extremes and the so-called ”normal” child The number of mentally defective individuals in a population will depend upon the standard arbitrarily set up as to what constitutes enius It is exactly as we should undertake to classify all people into the three groups: abnormally tall, normally tall, and abnormally short[20]
[20] See Chapter VI for discussion of the significance of various I Q's
2 The common opinion that extreme deviations below the median are more frequent than extreme deviations above theunselected school children, at least, for every child of any given degree of deficiency there is another child as far above the average I Q as the former is below We have shown elsewhere the serious consequences of neglect of this fact[21]
[21] See p 12 _ff_
3 The traditional view that variability inadolescence is here contradicted, as far as intelligence is concerned, for the distribution of I Q's is practically the sae from 5 to 14 For example, 6-year-olds differ from one another fully as much as do 14-year-olds
THE VALIDITY OF THE INTELLIGENCE QUOTIENT The facts presented above argue strongly for the validity of the I Q as an expression of a child's intelligence status This follows necessarily froes The inference is that a child's I Q, as measured by this scale, remains relatively constant Re-tests of the same children at intervals of two to five years support the inference Children of superior intelligence do not seeet older, nor dull children to develop average intelligence
Knowing a child's I Q, we can predict with a fair degree of accuracy the course of his later developless if considered apart froe It is only the ratio of retardation or acceleration to chronological age (that is, the I Q) which has significance
It follows also that if the I Q is a valid expression of intelligence, as it seerade method” becomes transformed automatically into a ”point-scale method,” if one wants to use it that way As such it is superior to any other point scale that has been proposed, because it includes a larger nu[22]
[22] For discussion of the supposed advantages of the ”point-scale es: _A New Point Scale for Measuring Mental Ability_ (Warwick and York, 1915)
sex DIFFERENCES The question as to the relative intelligence of the sexes is one of perennial interest and great social importance The ancient hypothesis, the one which dates from the time when only men concerned theranted the superiority of the y, however, it was soon found that as far as the evidence of ence of woh as that of men and boys
If we accept this result we are then confronted with the difficult proble an explanation for the fact that so few of those who have acquired eminence in the various intellectual fields have been women Two explanations have been proposed: (1) That women become eminent less often than men simply for lack of opportunity and stience of the sexes is the same, extreme variations may be more common in males It is pointed out that not only are there more eminent men than eminent women, but that statistics also show a preponderance of ly it is often said that woe, while e of distribution
[Illustration: FIG 3 MEDIAN I Q OF 457 BOYS (UNBROKEN LINE) AND 448 GIRLS (DOTTED LINE) FOR THE AGES 5-14 YEARS]
Many hundreds of articles and books of popular or quasi-scientific nature have been written on one aspect or another of this question of sex difference in intelligence; but all such theoretical discussions taken together are worth less than the results of one good experiment