Sex and intelligence

Sex differences in psychology or gender differences are differences in the mental functions and behaviors of the sexes, and are due to a complex interplay of biological, developmental, and cultural factors. Differences have been found in a variety of fields such as mental health, cognitive abilities, personality, and tendency towards aggression. Such variation may be both innate or learned and is often very difficult to distinguish. Modern research attempts to distinguish between such differences, and to analyze any ethical concerns raised. Since behavior is a result of interactions between nature and nurture researchers are interested in investigating how biology and environment interact to produce such differences, although this is often not possible.

A number of factors combine to influence the development of sex differences, including genetics and epigenetics; differences in brain structure and function; hormones; or differences in psychological traits such as emotion, motivation, cognition, and sexuality. Differences in socialization of males and females may decrease or increase the size of sex differences.

Beliefs about sex differences have likely existed through the entire history of humanity. In his 1859 book On the Origin of Species Charles Darwin proposed that, like physical traits, psychological traits evolve through the process of sexual selection:

In the distant future I see open fields for far more important researches. Psychology will be based on a new foundation, that of the necessary acquirement of each mental power and capacity by gradation.

Two of his later books, The Descent of Man, and Selection in Relation to Sex (1871) and The Expression of the Emotions in Man and Animals (1872) explore the subject of psychological differences between the sexes. The The Descent of Man and Selection in Relation to Sex includes 70 pages on sexual selection in human evolution, some of which concerns psychological traits.

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