Organizational-Activational Hypothesis of Hormones Organizational –Early development Prenatal in humans Perinatal in rodents –Produces permanent changes in tissue organization (neurogenesis) Genital Tract Genitalia Brain Circuits: this is controversial because of gender stereotypes –However, some recent evidence of organizational effects at puberty Activational –Also called permissive –After early development –Modulating cell growth and activity –Changes in neural activity

The Aromatization Hypothesis

Organizational Hypothesis applied to Brain circuits Prenatal testosterone –organizational effects on genitalia in (XY) males and (XX) females (CAH example) –disrupts the lordosis behavior of (XY) female rats –Phoenix (1959) suggested that brain circuits are also organized by prenatal testosterone –Called “masculinizing the brain” –Has effects on nonreproductive behaviors As seen in CAH example Type of aggressive behavior Type of play behavior Maybe sexual orientation

Brain Anatomy Gender Differences Hypothalamus –sexually dimorphic nucleus of the preoptic area –Regulation of FSH and LH Corpus Collasum –Some reports of more connections between hemispheres in women but other studies report no differences Differences in laterality of activation during language tasks –Some studies find differences other studies do not –More bilateral brain activation among women is reported in the inferior frontal gyrus posterior regions of the middle/superior temporal gyrus –small sex-by-age interactions in frontal and temporal regions on three of four language tasks –differences are small, task-specific, and acquired during development Note: these are phenotypic differences, brain circuits are influenced by an interaction of genetics and experience

A View of Sexual Dimorphism in the Human Brain Many parts of the human brain are sexually dimorphic. The question arises—are these dimorphisms caused by prenatal hormone exposure or by social influence?

Behavioral Gender Difference Preferences for toys –Girls prefer dolls –Boys prefer trucks –Present in infants –Seen in non-human primates –Related to prenatal androgen exposure, CAH example Play style –Boys more rough and tumble –Girls more nurturing –Also reported in a few studies with monkeys –It is not about the type of toy Boys do rough and tumble play with dolls Girls do nurturing play with fire trucks Aggressive behavior –Men use more physical aggression –Women use more relational “indirect” aggression Note: These are gender differences, phenotypic differences

Cognitive Gender Difference Most of these differences are small –however most psychological studies have small differences They are average differences so they do not speak to an individual’s cognitive ability All of them can be modified with experience –Men can improve language –Women can improve spatial rotation Women better then Men –Matching items –Spatial location of objects –Word recall –Fine-motor coordination –Math calculations Men better then Women –Rotational Spatial Tasks –Navigational skills –Throwing motor skills –Matching line slope –Math reasoning See next slide for examples of language differences

Gender differences in language processing Learning to speak a new languages –Easier for women –prevalence of preverbal skills and spontaneous language among small girls. Language production –female advantage in, verbal fluency –male advantage in the comprehension of verbal analogy Women better in –Spelling –language ability –grammatical usage –verbal memory for specific lists of unrelated words Digits paragraph content

Disputing Biological influence on Gender Differences Recently four semi-scholarly books have appeared, purporting to show that sex differences are primarily socially constructed –Delusions of Gender (2010) by Cordelia Fine –Brainstorm (2010) by Rebecca Jordan-Young –Pink Brain, Blue Brain (2009) by Lise Eliot –The Truth About Girls and Boys (2011) by Caryl Rivers and Rosalind C. Barnett These authors all claim that sex differences at birth are negligible, but that our sexist society teaches girls and boys to be different. Longitudinal study (Raznahana, 2010) found significant sex differences in the structure of the cerebral cortex although the differences diminish as a function of age, from age 9 through age 22. See movie clip of changes to cortex over this time period.Raznahana, 2010movie clip

What is Gender? From the Middle English gendre from Latin genus. which means 'kind', 'type', or 'sort'. –but it is not a type, not an either or –Individuals are more or less masculine or feminine –commonly used interchangeably with sex which is confusing because sex is a type Male sex – genetic XY – anatomically penis and testes Female sex- genetic XX – anatomically vagina and ovaries However some individuals are Intersex –Gender development begins at conception –Gender Identity: an individual's self-conception distinguished from actual biological sex –XY Person with prenatal T, testes and penis could identify as a women –XX person with no prenatal T, ovaries and vagina could identify as a man –Not the same as sexual orientation

What Determines Gender? Genetic sex –XX - Female –XY - Male Social Environment –Pressure to fit a particular gender stereotype Both: across several sensitive periods during development –Fetal –Early Childhood (pre pubertal) –Adolescences (post pubertal) Gender is a Phenotype –Genotype/Environment Interaction produces Phenotypes

What Determines Gender? Can a person with XY genetics be socialized to be a girl? –Sex Reassignment examples Surgery to remove the penis and construct a vulva Raised as a girl, i.e. sex reassignment Malformed penis (cloacal exstrophy) –Many reported cases –about 50 percent reject sex reassignment Penis damaged during circumcision –Two reported cases »1. John/Joan – famous case- complete rejection of reassignment »2. Earlier reassignment with gender identity accepted but masculine preference for play behavior

What Determines Gender? Can a person with XY genetics be socialized to be a girl? –Guevedoces: because of no 5 alpha reductase Can not convert T to DHT Have prenatal organizational effects of T but not DHT –i.e. brain circuits are masculinized Ambiguous genitalia at birth so they are raised as girls Increased T at puberty: male secondary sex characteristics Change to male gender identity –Androgen Insensitivity Syndrome (AIS): no androgen receptors Prenatal T exposure but –Male genitalia do not develop –brain circuits are not masculinized raised as a girl and always accept gender identity typical feminine preferences

Guevedoces

Quigley scale for androgen insensitivity syndrome grades 1 through 6, are differentiated by the degree of genital masculinization; grade 1 is indicated when the external genitalia is fully masculinized grade 6 is indicated when the external genitalia is fully feminized grades 2 through 5 quantify four degrees of increasingly feminized genitalia that lie in the interim. Grade 7 is indistinguishable from grade 6 until puberty and is thereafter differentiated by the presence of secondary terminal hair grade 6 is indicated when secondary terminal hair is present whereas grade 7 is indicated when it is absent.

Androgen-Insensitive Women

An Androgen-Insensitive Person

What Determines Gender? Will prenatal exposure to testosterone make a person with XX genetics into a man? CAH females compared to other women –Tomboys – a little more rough and tumble play –Better at spatial task –Usually heterosexual but slightly more Homosexual sexual activity –Less interest in having a family –Weaker gender identity –Show less empathy –Have more physical aggression

Normal Female Genitalia

An Intersex Phenotype

Normal Male Genitalia

What is sexual Orientation? Categories of sexual orientation –Heterosexuality: attracted to different sex/gender –Homosexuality: attracted to same sex/gender –Bisexuality: attracted to either sex/gender Based on the sex and or gender of the persons whom the individual finds sexually attractive Do not confuse with gender identity –Gay men are not women trapped in a man’s body –Lesbians are not men trapped in a women’s body –Gender identity and sexual orientation can be independent characteristics of sexuality

What Determines a Person’s Sexual Orientation? Influence of prenatal androgen exposure –Genetic male (XY) mostly Heterosexual a small percent of Homosexual or Bisexual AIS individuals also mostly Hetero –female gender identity so they prefer men –Genetic female (XX) mostly Heterosexual a small percent of Homosexual or Bisexual CAH individuals slight increase in Homosexual and Bisexual Genetics of sexual orientation –Several studies have reported higher concodance rates of Homosexuality in dizygotic versus monzygotic twins –A few studies have reported genetic makers in comparisons of DNA

Exotic Becomes Erotic Biological variables such as genes or prenatal hormones influence temperament Temperament predispose him or her to enjoy some activities Prefer to play with peers who share their activity preferences –Boys prefer more rough and tumble play Gender-conforming children will feel different from opposite-sex peers

Exotic Becomes Erotic Gender-nonconforming children will feel different from same-sex peers –Recent studies indicate that nonconforming children are more likely to be homosexual Feelings of being different produce heightened physiological arousal Childhood arousal is subsequently transformed into erotic attraction