Why%20do%20we%20have%20particular%20preferences?

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Sexual Behaviors

• Why do we have particular preferences?
• Evolutionary Explanations
• Sex differences? Psychoneuroendocrinology

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Evolutionary explanations

• Preferences/behaviors and choices..

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1871 evolution of characteristics that give
organisms a reproductive advantage Survival of
the fittest definition of survival
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• Sexual selection based on parental investment by
  each sex
• kin selection
• certain wasp species certain bird species
• E.O. Wilson

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thinking about parental investment and sexual
selection

• 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

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

• amount of time for a woman
• amount of time for a man -

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

• females

• males

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Problems with evolutionary explanations for
behavior

• always use posthoc observations to explain
  behavior
• never can be really proven

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David Buss

• The Evolution of Desire Strategies of Human
  Mating
• has looked at preferences across MANY cultures
  from around the world with specific
  predictions..

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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 scale
• 1 not at all currently seeking
• 7 strongly currently seeking

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Hypothesis

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

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From Buss and Schmitt, 1993
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Hypothesis

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

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From Buss and Schmitt, 1993
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Clark and Hatfield, 1989

• Attractive confederate approaches students on
  University of Hawaii campus
• I have been noticing you around campus, I find
  you very attractive..
• Would you go out with me tonight?
• Would you come over to my apartment tonight?
• Would you go to bed with me tonight?

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Some other hypotheses

• Importance of financial prospects

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Some other hypotheses

• Age of partner

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role of hormones in sexual development and
behavior

• What is a hormone?
• chemical substance released that binds to
  receptors on other cells
• How is this different from a neurotransmitter?

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Some chemicals act as both neurotransmitters AND
hormones
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role of hormones in sexual development and
behavior

• 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

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Steroid hormones

• 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

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

• organizational effects
• critical window for organizational effects
  (usually early in development)

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

• organizational effects
• critical window for organizational effects
• effects are usually permanent
• primary sexual characteristics
• structural AND CNS circuitry

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• Activational Effects
• activating established circuits
• effects are reversible and usually occur after
  puberty
• secondary sexual characteristics

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So what happens to determine genotypic and
phenotypic sex?

• genotypic sex vs phenotypic sex
• genotypic sex - determined at time of
  fertilization

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23rd chromosome is sex chromosome
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• phenotypic sex
• what you see

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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

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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

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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

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• 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

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• "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

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So what are some things that can go wrong?

• 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

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Congenital Adrenal Hyperplasia

• 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

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5 alpha reductase deficiency

• 5 alpha reductase is the enzyme that produces the
  androgen DHT (dihydrotestosterone)
• DHT is important (apparently) for the production
  of male external genitals

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• 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?

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true hermaphroditism

• 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

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What about organizational effects other than sex
organs?

• 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

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Example of experiments
organizational activational behavior




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organizational activational behavior
castrate male give T no sex no aggression
castrate T inj no T no sex no aggression
castrate T inj give T injections typical male behavior
T normal castrate as adult little sex little aggression
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In utero position

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

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0M, 1M and 2M females exposed to varying levels
of male hormones from developing sib nearby
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Sexually dimorphic behaviors

• 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

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• 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?

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What are some alternative explanations?
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Controversies in the application of activational
effects of testosterone

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

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• 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

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Controversies in the application of activational
effects of testosterone

• 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

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• 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

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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.
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• 1996 California became the first state to pass
  chemical castration law

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• 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

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Chemical castration?

• 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

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Are there data that support it?

• 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

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Medical Side Effects

• 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