1. Sexual Development
Module 53

2. Discovering Psy2e photo p. 328

3. Sex Linked Traits
For males, the smaller Y chromosome often does not contain a corresponding gene segment to match the one on the X chromosome.
This means that a male can display certain recessive characteristics as the result of having only one recessive gene carried on the X chromosome of his XY pair.
Traits determined by recessive genes on the X chromosomes are referred to as sex-linked recessive characteristics
Color blindness, baldness, hemophilia, Fragile X
Thanks Mom!

4. Hormones & the Developing Brain
At about 7 weeks, a gene turns on the production of testosterone by the testes in males.
Estrogen is produced in females by the ovaries.
During 4th & 5th months, the fetal brain’s wiring is influenced by these hormones.
this is when one get’s “wired” male or female

5. ADOLESCENT SEXUAL DEVELOPMENT
Puberty – 2 year rapid period of sexual development ending with reproductive maturity

6. Intersex
Intersex – born with intermediate or unusual combination of male & female physical features.
Born a Boy, Brought Up a Girl: The David Reimer Story – watch this documentary to see what life was like for a boy raised like a girl after a botched circumcision.
(4 part series – 10 minutes each)

7. Consequences of Sexual Behaviors
Sexually Transmitted Infections (STIs)
2/3 of new infections in people under 25
39.5% of sexually experienced year old females had an STI
Overconfidence & combination of attraction & alcohol at times all contribute to risky behavior.
Americans have higher rates of teen pregnancy & STIs than Europeans? What environmental factors contribute to this?
Factors Contributing to
Teen Pregnancy:
Minimal communication on birth control
Guilt related to sexual activity (makes one less likely to be prepared)
Alcohol Use
Mass Media norms of unprotected promiscuity with no repercussions
Factors Predicting to Sexual Restraint:
High Intelligence
Religious Engagement
Father Presence
Participation in service learning programs (volunteering to help others)

8. Sexual Orientation

9. Sexual Orientation
Sexual orientation—direction of a person's emotional and sexual attractions
Heterosexual—sexual attraction for the opposite sex
Homosexual—sexual attraction for the same sex
Gay—typically used to describe male homosexuals
Lesbian—typically used to describe female homosexuals
3% of men, 1-2% of women
Bisexual—sexual attraction for both sexes
Less than 1%
Questioning – unsure of their sexual orientation

10. Psychological History
of Sexual Orientation
Psychologists agree that sexual orientation is not chosen or willfully changed.
1973 – Homosexuality removed from the list of “mental illnesses” by the APA.
“Efforts to change sexual orientation are unlikely to be successful and involve some risk of harm.”
Compared to men’s sexual orientation, women’s tends to be less strongly felt and more variable (erotic plasticity).

11. Biology & Sexual Orientation
No evidence supports that certain environments make it more or less likely a person will be homosexual or heterosexual
(e.g., parenting, abuse, sexual experience)
Many examples of other animals showing homosexual behavior
Brain structure—differences found in tiny cluster of neurons in the hypothalamus of homosexual and heterosexual men
In homosexual men and heterosexual women, the cluster was only half the size as in heterosexual men
Same difference is found in homosexual sheep
When straight women smelled a scent from male sweat their hypothalamus light up. Same thing happened when gay men smelled the sweat. Straight men’s brains had no reaction.
Genetics—evidence from twin studies suggests that genetics play a role
52% of identical twins, 22% of fraternal twins, 11% of adoptive brothers
Changing one gene in a fruit fly can alter their sexual orientation
Older-Brother/Fraternal birth-order - Link to having older brothers? See ABC News Clip

12. Other General Findings
Findings suggest a possible relationship among prenatal stress, androgens, and the development of brain systems that play a role in sexual attraction
Children who are raised by gay or lesbian parents are as well adjusted as children who are raised by heterosexual parents. They are no more likely to be gay or lesbian in adulthood
Sexual orientation is an early-emerging (as early as age six), ingrained aspect of the self that probably does not change.
See ABC News clip on Genetic Links to Being Gay.
Male and female homosexuals are less likely than heterosexuals to have followed the typical pattern of gender-specific behaviors in childhood
Once sexual orientation is established, whether heterosexual or homosexual, it is highly resistant to change.
Gays and lesbians can be found in every occupation and at every socioeconomic level in our society.