Whether we define intelligence in terms ofg,
separate abilities, or hierarchical relationships among
factors, society ultimately decides which abilities will
be valued, rewarded, and nurtured. Perhaps this is
why all intelligence tests seem so much alike. They
are designed to predict what society values. Our soci-
ety tends to reward verbal ability, reasoning, reading,
information acquisition, analytic ability, and so on.
School Success. In general, IQs have been shown
to relate substantially bothtosuccessinschoolandto
achievement tests that measure what has been learned
(Deary et al., 2010; Hunt, 2011; Kamphaus, 1993;
Ones, Viswesvaran, & Dilchert, 2005). The correla-
tion between IQ scores and grades is about .50
(Neisser et al., 1996). It seems apparent that success
in school is related to a host of variables, including
motivation, teacher expectations, cultural back-
ground, attitudes of parents, and many others. We
are then confronted with the very difficult clinical
task of sorting out those variables. When success or
failure in school occurs, is it because of intelligence,
motivation, cultural background, or what? Any
behavior is complexly determined by many variables
other than just general or specific intelligence.
Occupational Status and Success. Because
amount of education would seem to be, in general,
a strong determinant of the kind of job one can
obtain, it will come as no surprise to learn that IQ
and occupational status are related. This relationship
seems to be true whether occupational status is
defined in terms of income, rated prestige, or social
prestige, or regardless of gender or ethnicity (Ones
et al., 2005). Interestingly, however, intelligence
scores also appear to be good predictors of job per-
formance (Hunt, 2011; Neisser et al., 1996; Ones
et al., 2005); IQ scores outperform predictors such as
biographical data, reference checks, education, and
college grades. However, once entry to a profession
has been gained, the degree of intelligence may not
separate the more eminent from the less eminent.
Apparently, some minimum level of ability is neces-
sary to achieve entry to or minimal performance in a
given occupation (though this may be debatable).
Once an individual gains entry, however, the degree
of subsequent success may be more a function of
nonintellectual factors.Demographic Group Differences. Although
most studies find few if any significant differences
between males and females in overall IQ scores, sig-
nificant differences between the sexes have been
obtained for specific abilities (Hunt, 2011; Neisser
et al., 1996). Males tend to score significantly higher
on measures of spatial ability and, after puberty, on
measures of quantitative ability. Females tend to
score significantly higher on measures of verbal abil-
ity (Neisser et al., 1996). Among racial/ethnic
groups, Hispanic Americans and African Americans
in North America tend to obtain significantly lower
IQ scores than do European Americans in North
America (Hunt, 2011; Neisser et al., 1996; Ones
et al., 2005). These findings, although consistent,
have been the source of much controversy. Neisser
et al. (1996) point out that although we do not
know what causes these ethnic/racial differences,
the size of the differences are within a range that
could be accounted for by environmental factors,
such as differential opportunities and resources avail-
able to youth from different ethnic backgrounds in
North America. More research is needed in this area
to provide insight into the nature of these ethnic/
racial differences. Despite the differences, however,
IQ scores remain good predictors of school, college,
and work achievement among Hispanic Americans
and African Americans (Ones et al., 2005).Heredity and Stability of IQ Scores
Heritability of Intelligence. In contrast to the
situation half a century ago, almost all psychologists
now acknowledge that intelligence is influenced, at
least in part, by genetic factors (Deary et al., 2010;
Hunt, 2011; Neisser et al., 1996; Petrill, 2005). The
reason for this reversal of opinion is the large body
of empirical evidence provided bybehavioral genetics
studies over the past several decades (McGue,
Bouchard, Iacono, & Lykken, 1993; Plomin,
DeFries, McClearn, & McGuffin, 2008). Box 7-2
presents a brief overview of the methods of behav-
ioral genetics.THE ASSESSMENT OF INTELLIGENCE 201