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

Physical Environment and Mental Development 335
these groups and the placebo group there was a significant
(P< 0-001) decline of 3-04 IQ points between ages 3 and 4. Thus,
while the dietary supplements did raise IQ several points over
the placebo group, they did not prevent the lowering of IQ between
ages 3 and 4. This rapid decline within a one-year period, in
addition to the fact that IQ at age 4 accounts for something less
than 50 percent of the IQ variance in late adolescence, makes this
study inconclusive as to whether any lasting effects on IQ were
derived from the dietary supplements during pregnancy. The
IQs of the children at ages 3 and 4 were within the typical
range for this population, and the decline in IQ from 3 to 4 is
also typical; studies of similar groups have found average declines
of about 10 IQ points between 3 and 6 years of age (Shuey, 1966,
pp. 6-31).
The second study takes a still different approach, which consisted
not of looking for children showing malnutrition and
determining their psychological characteristics, but rather of
finding children in the poorest families in the poorest slums of a
large Southern city, Nashville, Tennessee (Carter, Gilmer,
Vanderzwaag & Massey, 1971). The investigators visited community
agencies to find out the location of poverty areas and to
identify poverty families. These areas were then explored by car,
followed by house-to-house canvassing by a social worker to find
the most impoverished families with children of certain ages. The
groups finally selected came from two housing projects on the
East side of Nashville.4 The criteria for selection included: mother
under 35 years of age, the target child should not be farther along
in the family than the third child, and younger siblings should be
present. Since the medical, nutritional, and psychological assessments
were intended to be extremely thorough and elaborate, only
19 families were selected, 10 Negro and 9 white. The target
children (singled out for special intensive study and enrolment
in an experimental preschool program) were between the ages of
3 years 8 months and 4 years 8 months. The authors describe in
general terms the typical backgrounds of the white and Negro
families from which their samples were drawn:
The typical family of a white child . . . is likely to be one in
which the natural father is present in the home at least 50 percent
of the time. He is usually an unskilled laborer or perhaps