Why do we have particular preferences?◦ Evolutionary Explanations

Sex differences? Psychoneuroendocrinology

Sexual Behaviors

Preferences/behaviors and choices…..

Evolutionary explanations

1871 – evolution of characteristics that give organisms a reproductive advantage

“Survival of the fittest” –definition of survival

Sexual selection based on parental investment by each sex◦ kin selection

certain wasp species; certain bird species E.O. Wilson

The sex that invests more in offspring should be more choosy or discriminating

The sex that invests less in offspring should compete more vigorously for opposite sex

thinking about parental investment and sexual selection

amount of time for a woman –

amount of time for a man -

Are there differences in the time investment in humans to produce an offspring?

If there are differences – should the strategy for what one looks for be different?

females males

If there are differences – should the strategy for what one looks for be different?

always use posthoc observations to explain behavior

never can be really proven

Problems with evolutionary explanations for behavior

“The Evolution of Desire: Strategies of Human Mating”

has looked at preferences across MANY cultures from around the world with specific predictions……..

David Buss

Hypothesis: Men will express greater desire for, or interest in, short-term mates than women

n= 148 college students; 75 men, 73 women

Asked if seeking short-term mate (“ one night stand, brief affair) and independently whether they were seeking a long-term mate (defined as marrige partner)

7 point scale1 – not at all currently seeking

7 – strongly currently seeking

David Buss

For any given period of time, men will desire a larger number of mates than will women

Hypothesis

From Buss and Schmitt, 1993

Which sex would more likely consent to sexual intercourse after knowing the other for a shorter period of time?

Hypothesis

From Buss and Schmitt, 1993

Attractive confederate approaches students on University of Hawaii campus

“I have been noticing you around campus, I find you very attractive”…..

a. Would you go out with me tonight?b. Would you come over to my apartment

tonight?c. Would you go to bed with me tonight?

Clark and Hatfield, 1989

Importance of financial prospects

Some other hypotheses

Age of partner

Some other hypotheses

What is a hormone?◦ chemical substance released that binds to

receptors on other cells

How is this different from a neurotransmitter?

role of hormones in sexual development and behavior

Some chemicals act as both neurotransmitters AND hormones

What is a hormone?◦ chemical substance released that binds to

receptors on other cells

How is this different from a neurotransmitter?◦ travels further distance◦ released by glands

role of hormones in sexual development and behavior

critical for aspects of sexual behavior (and development of sex organs and circuits)

ex. estrogen, testosterone,

these are lipid (fat) soluble and readily cross membranes and so can even bind to receptors in neuronal and cell nuclei

Steroid hormones

1. organizational effects• critical window for organizational effects

(usually early in development)

Steroid hormones exert effects on behaviors and/or structures in 2 ways

1. organizational effects• critical window for organizational effects

effects are usually permanent primary sexual characteristics

• structural AND CNS circuitry

Steroid hormones exert effects on behaviors and/or structures in 2 ways

2. Activational Effects• activating established circuits• effects are reversible and usually occur after

puberty• secondary sexual characteristics

genotypic sex vs phenotypic sex ◦ genotypic sex - determined at time of

fertilization

So what happens to determine genotypic and phenotypic sex?

23rd chromosome is sex chromosome

phenotypic sex – ◦ what you see………

Y chromosome controls development of gonads

gonads – sex organs that releases steroid hormones (for males; testes for females; ovaries)

on Y chromosome is a gene - HY antigen ◦ if present- testes will develop ~ 6 weeks after

conception

Importance of Y chromosome:

Y chromosome controls development of gonads gonads – sex organs that releases steroid

hormones (for males; testes for females; ovaries)

on Y chromosome protein is produced- HY antigen ◦ if present testes will develop ~ 6 weeks after

conception◦ if not present – ovaries will develop

Importance of Y chromosome:

Y chromosome controls development of gonads gonads – sex organs that releases steroid

hormones (for males; testes for females; ovaries)

on Y chromosome is a gene - HY antigen ◦ if present testes will develop ~ 6 weeks after

conception◦ if not present – ovaries will develop

◦ up until that time a single “premordial” tissue is identical in male and females

Importance of Y chromosome:

What if this gene inadvertently goes onto an X chromosome?◦ XX male – estimated 1 in 20,000

What if this gene is missing from a male?◦ XY female- estimated 1 in 20,000

"Nature's impulse is to create a female“◦ in the absence of HY antigen (early) or male sex

hormones (later in prenatal development), the organism will develop as female

◦ male hormones (androgens like testosterone and dihydrotesterone) are necessary for undeveloped tissue to develop into male internal and external sex organs

AIS – androgen insensitivity syndrome◦ a genetic abnormality whereby there are

androgen receptors but they do not respond to androgens

females – little body hair males – internal gonads – testes;

what after that? 1 in 65,000 males estimated

often diagnosed at puberty

So what are some things that can go wrong?

estimates 1 in 13,000 to 1 in 16,000 overactive adrenal gland releases excess

androgens diagnosed in females at birth – because of

ambiguous genitalia males not usually diagnosed at birth

Congenital Adrenal Hyperplasia

5 alpha reductase is the enzyme that produces the androgen DHT (dihydrotestosterone)

DHT is important (apparently) for the production of male external genitals

5 alpha reductase deficiency

guave doces; Dominican Republic◦ first reported in 1974

early cases – first raised as girls……… What does it say about biology vs vs

environment for determining human sex roles?

intersex condition in which indvl born with ovarian and testicular tissue

can be one on one side; the other on the other or more often one or both gonads is an “ovotestis” containing both

very rare

can see XXY, XX/XY, XX XXY

true hermaphroditism

CNS – clearly affected by both organizational and activational effects of steroid hormones

Rodents have been used to gain a tremendous amount of info about the role of organizational and activational effects of steroid hormones

What about organizational effects other than sex organs?

Example of experiments

organizational activational behavior

organizational activational behavior

castrate male give T no sexno aggression

castrate + T inj

no T no sexno aggression

castrate + T inj

give T injections

typical male behavior

T normal castrate as adult

little sexlittle aggression

In species that have multiple births; developing embryos can be affected by hormones from surrounding fetuses

In utero position

0M, 1M and 2Mfemales; exposedto varying levels ofmale hormones from developing sib nearby

aggression male sexual

behavior rough-and-tumble

play sexual

attractiveness onset of puberty AG distance

differences in all of these behaviors depending on whether it is a 0M or 2M female

Sexually dimorphic behaviors

so data from numerous species that bear multiple offspring at the same time, prenatal hormones can have an influence on later structures and behavior!

What about human conditions?

What are some alternative explanations?

What role does activational effects of T play on male sexual behavior?

Controversies in the application of activational effects of testosterone

So organizational effects of steroid hormones are critical for setting up circuitry for behaviors that are “sexually dimorphic” and activational effects are critical for activating the circuits in lower animals –

What role do activational effects of T play on male sexual behavior?

◦ in rats and lower species – obvious

◦ in humans – somewhat less obvious but definitely still important

Controversies in the application of activational effects of testosterone

McQuay◦ a former school bus driver in prison in TX for

sexually attacking a young boy (1989)◦ 1995 – as he approached parole asked state of TX

to be castrated; claimed he would repeat the crimes if not castrated attempted it himself in cell with a razor lots of people volunteered the money for the cost of

surgery

In a letter to the editor published in The Dallas Morning News on Sunday, McQuay said he expects to be released soon because of his clean disciplinary record.

"... I will be required to look for work and so forth, meaning I will be walking the streets of your city, your community, your neighborhoods," McQuay wrote.

"And without a doubt, there will be children around. You tell me what is likely to happen if I am not castrated before I am released.“

1996 – California became the first state to pass chemical castration law

1996 – California became the first state to pass chemical castration law◦ requires chemical castration of any person found

guilty a 2nd time of specified sex offenses◦ Florida, Georgia, Louisiana, Montana, Oregon,

Texas and Wisconsin followed shortly thereafter with similar laws

Depo-Provera –◦ lowers testosterone and resulting sex drive in

men◦ originally (and still used) as female contraceptive◦ most states say that repeat offenders may be

offered it as a condition for their parole

Chemical castration?

Danish study◦ 5 out of 117 castrated sex offenders relapsed

over an 18 year period, 1/10th of the rate of non castrated offenders

Depro-Provera cut recidivism rates of pedophiles in California, Texas, and some European countries using it.

Some studies suggest that recidivism falls to 5%; sexual fantasies are lessened

Are there data that support it?

some may not be able to tolerate med◦ headaches, nausea, high blood pressure, possible

diabetes, gallstones, hypertension, increased risk of stroke, loss of bone density

some that have been on it for years must go off

Medical Side Effects