Sex and the Brain
Sex is Complex
Sex – a person’s genetic biological characteristics:
Male, female, a continuum between the two
Sexual orientation – who you are attracted to:
Opposite sex
Same sex
Both, neither
Gender – social roles assigned by biological sex.
Sexual identity – which sex you feel you are,
independent of biology.
Transsexuals, transvestites
Sexual Behavior
Phases of sexual response are the same across
species.
Behavior results from many circuits,
including hypothalamic activation,
environmental inputs, hormones.
The cortex decides what is and is not sexually
stimulating.
Sexual scripts – learned ways of responding in
sexual situations.
Human Sexual Response
Sexual Dimorphisms
Male and female brains differ because male
and female bodies differ.
The most distinct dimorphisms are related to
reproductive behaviors.
Many other sex differences have been claimed
in the literature but these do not hold up well.
Few cognitive differences exist in behavior once
the impact of culture/socialization is controlled.
Sex Differences Claimed
Women are better at verbal tasks – false.
Men are better at spatial tasks and math –
largely false.
Women are more emotional, men are less
emotional – false, except for expressivity.
Women talk more than men – false.
Men are more aggressive and more violent –
true.
Impact of Testosterone
Testosterone is not responsible for the
masculinization of the male brain.
Estrogen, binding to estradiol sites, results in
masculinization of a developing fetus.
Females do not produce surges of estrogen early
in development and so miss this stage.
Testosterone organizes masculinization early
on and is needed again to trigger puberty.
Male vs Female
Because hormones trigger masculinization, it
is possible to have male females (genetically
XX) and female males (genetically XY).
Genetic males with a defective androgen
receptor will develop as female.
Genetic females with congenital adrenal
hyperplasia (CAH) have unusually large
amounts of circulating androgens.
Homosexuality
Defined as sexual attraction to members of
the same sex.
Large-scale studies show that neither early
childhood experiences nor learning accounts
for homsexuality.
Postmortem studies suggest the SCN of the
hypothalamus may be responsible.
Hamer’s studies suggest a genetic basis.