Sexual Dimorphism in Homo sapiens
How large are differences between men and women? The table below shows the size of some well-known differences.
|
Variable |
Male Mean |
Female Mean |
d |
CL |
|
Verbal ACT |
17.9 |
18.9 |
0.19 |
55% |
|
Math ACT |
18.6 |
16.1 |
0.48 |
63% |
|
Aggressiveness |
9.3 |
6.9 |
0.62 |
67% |
|
Mental Rotation |
23 |
15 |
0.91 |
74% |
|
Weight |
163 |
134 |
1.07 |
78% |
|
Leg Strength |
212 |
94 |
1.66 |
91% |
|
Height |
69.7 |
64.3 |
2.00 |
92% |
The d statistic is the difference in standard deviation units. As you can see, the mean verbal ability (as measured by the American College Test) of women is about 1/5 standard deviation higher than that of men, a small but not trivial difference.
CL is the common language effect size statistic. It tells us the probability that a randomly selected score from the one population will be greater than a randomly sampled score from the other population. For Verbal Ability it tells us that if we were to randomly pair men and women, in 55% of the pairs the women would have greater verbal ability than the man.
The sex difference is math ability is larger than with verbal ability, with the mean score for men being about 3/5 of a standard deviation higher than that of women, a medium-sized difference. If you randomly paired men and women, in 67% of the pairs the man would have the greater math ability.
The sex difference in ability to perform mental rotations is even greater, about 9/10 of a standard deviation, a large effect.
The greatest differences shown in this table deal with physical characteristics, but there are behavioral characteristics on which sex differences are quite large too. For example, men and women differ very much with respect to attitudes about a variety of sexual behaviors.
CL: The Common Language Effect Size Statistic – more details on this statistic
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Dr. Karl L. Wuensch
This page most recently revised on the 16th of December, 2013.