This book describes the major differences between men and women in cognitive or problem-solving abilities and discusses the possible biological contributions to such differences. The book argues that sex differences in cognitive patterns and in motor skills arose out of complementary evolutionary histories of men and women and that evidence for socialization influences on such differences is meager. The book describes how most sex differences are a secondary consequence of the presence or absence of the Y chromosome and notes the presence of early sensitive time periods for masculinization of different behaviors. The book also presents research evidence related to sex differences in the areas of motor skills, spatial abilities, mathematical aptitude, perception, and verbal abilities. It further presents various behavioral, neurological, and endocrinological studies that illuminate the processes giving rise to these sex differences. The book concludes by noting that there are substantial stable sex differences in cognitive functions such as spatial rotation ability, mathematical reasoning, verbal memory, and in motor skills requiring accurate targeting and finger dexterity. The book's appendix explains basic statistics concepts; a glossary of relevant terms completes the volume. Each chapter contains references. (KB)