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

Intelligence and Educability 77
at higher grades, tests of reading comprehension, for those children
who have already mastered the basic skills, become more or less
indistinguishable in factorial composition from the so-called tests
of verbal intelligence. Similarly, tests of mechanical arithmetic
arithmetic computation) have less correlation with g than tests of
arithmetic thought problems, such as the Arithmetic Concepts
and Arithmetic Applications subtests of the Stanford Achievement
battery. Accordingly, most indices of scholastic performance
increasingly reflect general intelligence as children progress in
school. We found in one study, for example, that up to grade 6,
verbal and non-verbal intelligence tests could be factorially separated,
with the scholastic achievement tests lining up on the same
factor with verbal intelligence (Jensen, 1971a). But beyond grade 6
both the verbal and non-verbal tests, along with all the scholastic
achievement tests, amalgamated into a single large general factor
which no form of factor rotation could separate into smaller
components distinguishable as verbal intelligence v. non-verbal
intelligence v. scholastic achievement. By grades 7 and 8 the
Lorge-Thorndike Non-verbal IQ and Raven’s Progressive Matrices
are hardly distinguishable in their factor composition from the
tests of scholastic achievement. At the same time it is important to
recognize that the Lorge-Thorndike Non-verbal IQ and Raven’s
Matrices are not measuring scholastic attainment per se, as
demonstrated by the fact that totally illiterate and unschooled
persons can obtain high scores on these tests. Burt (1961a), for
example, reported the case of separated identical twins with widely
differing educational attainments (elementary school education v.
a university degree), who differed by only one IQ point on the
Progressive Matrices (127 v. 128).
Another important characteristic of the best intelligence test
items is that they clearly fall along an age scale. Items are thus
‘naturally’ ordered in difficulty. The Figure Copying Test is a
good example. The Figure Copying Test was developed at the
Gesell Institute of Child Study at Yale University as a means for
measuring developmental readiness for the traditional school
learning tasks of the primary grades. The test consists of the
ten geometric forms shown in Figure 3.1, arranged in order of
difficulty, which the child must simply copy, each on a separate
sheet of paper. The test involves no memory factor, since the figure
to be copied is before the child at all times. It is administered