While the general outline
of a pattern is inherited, these small characters do not seem to be, but
are apparently rather due to the stretching of the skin as it grows.
Illustration from J. H. Taylor.]
[Illustration: DISTRIBUTION OF I Q'S OF 905 UNSELECTED CHILDREN, 5-14
YEARS OF AGE
THE DISTRIBUTION OF INTELLIGENCE
FIG. 23.--Diagram showing the mentality of 905 unselected
children, 5 to 14 years of age, who may probably be taken as
representative of the whole population. The median or tallest column,
about one-third of the whole number, represents those who were normal
or, as a statistician would say, mediocre. Their mental ages and
chronological ages were practically identical. To the left of these the
diminishing columns show the number whose mental ages fell short of
their chronological ages. They are the mentally retarded, ranging all
the way down to the lowest one-third of one per cent who represent a
very low grade of feeble-mindedness. On the other side the mentally
superior show a similar distribution. A curve drawn over the tops of the
columns makes a good normal curve. "Since the frequency of the various
grades of intelligence decreases _gradually_ and at no point abruptly on
each side of the median, it is evident that there is no definite
dividing line between normality and feeble-mindedness, or between
normality and genius.
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