Sex differences in brain and behavioral development

Daily gender expression is associated with psychological adjustment for some people, but mainly men

“…This may reflect intentional reporting (e.g., self-directed gender policing), as two participants reported maximal sex-congruent scores every day. Finally, most daily fluctuations in gender expression were in gender-typical ranges, indicating that variation does not reflect “qualitative” shifts in gender identity, which shows a very large difference between men and women 45 .…”

“…Several features of the study design warrant comment. The between-person sample size may seem small, but gender expression is among the largest known sex differences 8 , 45 , and each participant provided up to 75 observations; thus, there was likely sufficient power to detect effects of interest, and effect sizes were consistently provided. Also, the sample consisted of young adults, did not include individuals across spectra of gender identities or clinical problems, and excluded individuals with known exogenous sex hormone alterations (i.e., oral contraceptive users) or missing data over 20%.…”

Evidence and Implications From a Natural Experiment of Prenatal Androgen Effects on Gendered Behavior

“…Psychological aspects of gender are neither monolithic nor absolute; people cannot be classified as female or male on the basis of one characteristic, or even a constellation of characteristics. Nevertheless, sex differences are among the largest effects in psychology (Beltz et al, 2020). Sex differences vary in size across characteristics: They are very large for choice of social partners (e.g., playmates and romantic partners), large for activity interests (e.g., childhood toy play, adult hobbies, occupations) and the incidence of some psychopathology (e.g., conduct disorder, depression), moderate for spatial abilities and some social behaviors (e.g., aggression), and small for personality; in comparison, sex differences in height are very large, and typical psychological effects are small to moderate.…”

“…Considerable attention has focused on neural mechanisms, but sex differences in the brain alone provide little information about the origins of psychological sex differences (for discussion, see Beltz et al, 2020). Behavior is subserved by the brain, so psychological sex differences are reflected in the brain.…”

From Genes to Behavior Through Sex Hormones and Socialization: The Example of Gender Development

“…Much work is directed to describing sex differences in brain structure and task activation, and neural 'signatures' could be considered endophenotypes for gender-related psychopathology; it is important to remember, however, that those differences might cause or result from psychological sex differences. Therefore, studies of hormonal influences on neural sex differences must also include behavioral measures and consider the dynamic nature of brain structure (for discussion, see Beltz et al, 2013).…”