It seemed like a simple task when I started writing this book. All I had to do was
provide a comprehensive synthesis of the theories and research concerning the
causes, correlates, and consequences of cognitive sex differences and make some
meaningful conclusions that were supported in the literature. My interest in the
area grew naturally out of several years of teaching both cognitive psychology and
psychology of women to college classes. The idea that women and men might ac-
tually think differently, that is have different preferred modes of thinking or differ-
ent thinking abilities, came up in both classes. At the time, it seemed clear to me
that any between-sex differences in thinking abilities were due to socialization
practices, artifacts and mistakes in the research, and bias and prejudice. After re-
viewing a pile of journal articles that stood several feet high and numerous books
and book chapters that dwarfed the stack of journal articles, I changed my mind.
The task I had undertaken certainly wasn't simple and the conclusions that I had
expected to make had to be revised.

The literature on sex differences in cognitive abilities is filled with inconsistent
findings, contradictory theories, and emotional claims that are unsupported by the
research. Yet, despite all of the noise in the data, clear and consistent messages
could be heard. There are real, and in some cases sizable, sex differences with re-
spect to some cognitive abilities. Socialization practices are undoubtedly impor-
tant, but there is also good evidence that biological sex differences play a role in
establishing and maintaining cognitive sex differences, a conclusion that I wasn't
prepared to make when I began reviewing the relevant literature.

The conclusions that I reached about cognitive sex differences are at odds with
those of other authors (e.g., Caplan, MacPherson & Tobin, 1985; Fairweather,
1976). There are probably several reasons why the conclusions in this review are dif-
ferent from the earlier ones. I believe that the data collected within the last few years

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