252 Chapter 7 Thinking and Intelligence
with young children; providing intense early educa-
tion; and sending children to preschool (Protzko,
Aronson, & Blair, 2013). In one study, attending
quality preschool increased the reading and math
skills of children from racial and ethnic minorities,
especially if they were not getting much cognitive
stimulation elsewhere (Tucker-Drob, 2012). And
two important longitudinal studies found that inner-
city children who got lots of early mental enrich-
ment at home and in preschool showed significant
IQ gains and had much better school achievement
than did children in a control group (Campbell &
Ramey, 1995; Reynolds et al., 2011).
Perhaps the best evidence for the importance
of environmental influences on intelligence is the
fact that in developed countries IQ scores have
been climbing steadily for several generations
(Flynn, 1987, 1999). (See Figure 7.7.) Genes can-
not possibly have changed enough to account for
these findings. Then what can? One possibility
is improvements in the education, health care,
diets, and job opportunities of the poorest, lowest-
scoring people, which increases the overall mean.
If that is so, we would expect to see large and rapid
increases in developing countries, and so we do. In
Kenya, IQ scores of rural 6- to 8-year-old children
jumped about 11 points between 1984 and 1998,
the fastest rise in a group’s average IQ scores ever
reported (Daley et al., 2003).
We see, then, that although heredity may pro-
vide the range of a child’s intellectual potential—a
Homer Simpson can never become an Einstein—
many other factors affect where in that range the
child will fall.Motivation, Hard Work, and
Intellectual Success LO 7.18
Even with a high IQ, emotional intelligence, and
practical know-how, you still might get nowhere
at all. Talent, unlike cream, does not inevitably
rise to the top; success also depends on drive and
determination.
Consider a finding from one of the longest-
running psychological studies ever conducted.
In 1921, Louis Terman and his associates began
following more than 1,500 children with IQ
scores in the top one percent of the distribution.
These boys and girls, nicknamed Termites after
Terman, started out bright, physically healthy,
sociable, and well adjusted. As they entered adult-
hood, most became successful in the traditional
ways of the times: men in careers and women as
homemakers (Sears & Barbee, 1977; Terman &
Oden, 1959). However, some gifted men failed
to live up to their early promise, dropping out of
school or drifting into low-level work. The 100children can be as high as 20 points (Stoch &
Smythe, 1963; Winick, Meyer, & Harris, 1975).
• Exposure to toxins. Many children, especially
poor and minority children, are exposed to dan-
gerous levels of lead from dust, contaminated
soil, lead paint, and old lead pipes, and lead can
damage the brain and nervous system. Even
children exposed to fairly low, supposedly safe
levels develop attention problems, have lower
IQ scores, and do worse in school than other
children (Hornung, Lanphear, & Dietrich, 2009;
Koller et al., 2004). In addition, children exposed
in utero to high levels of pesticides (still legal for
spraying on farm fields) later have an IQ score
that is 7 points lower on average than that of
children with the least exposure (Raloff, 2011).
• Stressful family experiences. Factors that pre-
dict reduced intellectual competence include
having a father who does not live with the fam-
ily; a mother with a history of mental illness;
parents with limited work skills; and stressful
events, such as domestic violence, early in life
(Sameroff et al., 1987). On average, each risk
factor reduces a child’s IQ score by 4 points.
• Living in severely disadvantaged and impover-
ished neighborhoods. When children grow up
in neighborhoods that are falling apart, are un-
safe, have high crime rates, and lack opportuni-
ties for education and exercise, their IQs decline
over time, even after they have moved to better
areas; the drop is comparable to that seen when
a child misses a year of school (Sampson, 2008).
In contrast, a healthy and stimulating environ-
ment can raise children’s IQ scores. Meta-analyses of
virtually all of the available controlled research show
that four interventions are clearly helpful: supple-
menting the diets of pregnant women and new-
borns with essential fatty acids; reading interactivelySevere poverty, exposure to toxic materials, run-down
neighborhoods, and stressful family circumstances can all
impede children’s cognitive development and lower their IQ.