114 Chapter 4the extent to which women had fewer edu-
cational and economic opportunities in a
country was associated with larger sex differ-
ences in math scores in favor of males.
By contrast, higher-stakes testing, such
as SAT data, shows that there is a small differ-
ence in math scores in favor of males (about
35 points) that has remained the same over
the past 35 years (Halpern et al., 2007). This
finding is interesting because it suggests that
the sex difference has persisted despite the fact
that more women are taking advanced math
courses in high school today than ever before.
However, it also is the case that more women
are taking the SAT today than ever before.
When sex differences in math are
found, researchers often point to the fact that
part of this overall effect is due to men be-
ing more likely than women to have really
high math scores. Men are more likely than
women to be in the very upper end of the
math distribution. However, Halpern and
colleagues (2007) caution that even this sta-
tistic is changing. Among those who scored
above 700 on the SAT math exam, the ratio
of male to female was 13:1 20 years ago, but
it is 2.8:1 today. There also is evidence that
men’s math scores are more variable than
women’s math scores (Halpern et al., 2007;
Hyde et al., 2008), and the reason for this is
not clear.
There is a paradox when it comes to
gender and math. Males perform better
than females on math achievement tests,
such as the SAT, but females receive better
math grades in school (Royer & Garofoli,
2005). Why do women perform better than
men in school? One reason may be that girls
and boys approach their schoolwork differ-
ently (Kenney-Benson et al., 2006). Girls
have a more mastery-oriented style (I do
math to improve my skills), whereas boys■ Although the sex difference in spatial skills does not ap-
pear to be changing over time, sex differences are more
likely to appear among older than younger children.
■ One domain in which women have better spatial skills
than men is object location.Mathematical Ability
Of all the cognitive domains, math is one
in which people seem to be confident of sex
differences. Two older meta-analytic re-
views from the 1990s concluded there was
a small sex difference in math ability favor-
ing males. In a meta-analysis of 100 stud-
ies on math skills, Hyde, Fennema, and
Lamon (1990) found an overall effect size of
d=+.15, favoring males over females but noted
that sex differences were decreasing with time.
The effect size in studies published before
1974 was+.31, whereas the effect size in stud-
ies published from 1974 onward was+.14. In
a meta-analysis of large samples of high school
students, Hedges and Nowell (1995) found an
average effect size ofd=+.16. Thus both re-
views concluded that there was an overall sex
difference in math in favor of males but that
the difference was small.
More recent data suggest that sex dif-
ferences in math aptitude have approached
zero. In an examination of statewide testing
in over 7 million students from 10 differ-
ent states, the overalldwas .0065, ranging
from-.02 to+.06 across grades 2 through
11, leading the authors to conclude that sex
differences in math aptitude have disap-
peared (Hyde et al., 2008). Research that has
examined women’s and men’s math perfor-
mance across 49 countries has shown many
effect sizes near zero (Else-quest, Hyde, &
Linn, 2010). This research also showed thatM04_HELG0185_04_SE_C04.indd 114 6/21/11 8:02 AM