Hormones & Sexual Behavior Lecture 26

Sexual Behavior: Rats n Controlled by sex hormones n Female l Proceptive ear wiggling, darting, hopping l Receptive - lordosis n Male l mounts l copulates ~

Organizational Effects of Hormones n SDN & SNB n Critical periods l Humans - prenatal l Rats - Perinatal easily manipulated ~

Hormones: Sexual Behavior n Gonadectomy l at birth n Adult males l testosterone  no male behavior l estrogen  lordosis n Adult females l estrogens  no female behavior l testosterone  male behavior ~

Human Sexual Behavior n No stereotypical M & F behaviors n Men are like rats l Testosterone: activational role n Women l Estrogens no activational effects l Testosterone levels correlated with frequency of intercourse ~

Homosexuality n Sex hormones role? l rats - yes l Humans? no difference in circulating hormones n Learning experiences? n or biologically determined?

Homosexuality n Simon LeVay l Brains of male AIDS victims l Anterior Hypothalamus l Anterior Commissure l Suprachiasmatic nucleus n SDN (rats) l Humans: 3rd interstitial nucleus of the Anterior Hypothalamus l INAH-3 ~

3d interstitial nucleus Volume mm n Anterior commissure larger in females l Similar relationship ~ F H-M M

Homosexuality: 2 Hypotheses n 1. Prenatal androgen levels l low in XY fetuses that  gay l high in XX fetuses  lesbian ~

2. Inherited Genes n MZ twin concordance approx. 50% l DZ twins approx. 20% n Xq28 - tip of the X chromosome l 33 of 40 pairs of gay brothers l fetal brain response to androgens ~ Homosexuality 2 Hypotheses

Nature vs. Nurture n John/Joan l penis destroyed during circumcision n 1960s - Gender deemed neutral at birth l constructed female genitalia l hormone treatment l 12 yrs old: positive results reported ~

Nature vs. Nurture n By 14 yrs old: living as male l reconstructive surgery l male hormone treatment l married by 25 n Reassessment in 1996 l rejected female role much earlier n Pendulum swings back toward nature l sex/gender not so malleable ~