Educability-and-Group-Differences-1973-by-Arthur-Robert-Jensen

34 Educability and Group Differences
his IQ 15 points.’ This kind of statement not only sidetracks
examination of the central question, but it also confuses the different
meanings and implications that an IQ difference of, say, 15
points can have for an individual and for a subpopulation. This is
a most important distinction.
For an individual, the addition or subtraction of 15 (‘true score’)
IQ points from his potential mental development will have quite
different consequences depending on the part of the range in
which the resultant IQ falls. Fifteen points added to an IQ of 70
could mean the difference between institutionalization or social
dependency and self-sufficiency in the world of work; 15 points
added to an IQ of 100 could mean the difference between failing
or succeeding in college. Since the standardized regression of
income on IQ is probably between 0*3 and 0*4, we can predict,
on the average, that along with a 15-point increase in IQ would
come an increase in income amounting to 0*3 or 0-4 standard
deviations on the scale of income. Also, the person with 15 points
added to his IQ, assuming the heritability of IQ remained the
same, would add, on the average, about 7 points to the IQs of his
(or her) children. And there would be many other individual
consequences of such a change in IQ. The reason we are not apt
to be very impressed by the observable differences between individuals
that result from a 15-point IQ difference is that we observe
specific cases rather than averages, and the correlation between
IQ and our various criteria of success is far from perfect. So we
note the very bright youngster who becomes a mediocre adult, and
his intellectually less favored classmate who becomes rich and
famous. Many factors other than intelligence obviously must play
an important part in a person’s career and fortunes, but there is
no reason to believe that on the average all these non-intellectual
factors will add up more favorably for those who are intellectually
less endowed than for those who are more endowed. If anything,
slightly the reverse is the case. There is a small but real positive
correlation between intelligence and other traits of personality
and character which favor success in our society. This should not
be too surprising. In an educational, occupational, and social
system that tends to sort out people according to their abilities, it
seems most likely that those traits of personality and temperament
which most complement and reinforce the development of intellectual
skills requiring persistent application, practice, freedom