Sex, Sexuality

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Sex, Sexuality Mating

• Differential reproduction is the engine that
  drives natural selection. Given that we
  reproduce sexually, natural selection should have
  designed adaptations for mating. Why isnt the
  study of mating a major area of psychology?
• Office hours
• Cosmides Thursdays, 230-330 Psych East 3808,
  Tuesdays 1230-130 HSSB 1010
• Mrazek Mondays, 1100-100pm, Bldg 429, room 102
  (mrazek_at_psych.ucsb.edu)
• Course website http//mentor.lscf.ucsb.edu/course
  /spring/psyc155
• E-res password collide

2
Sex, sexuality mating

• In sexually dimorphic species, how do biologists
  tell males from females?
• Sexual differentiation in humans
• Sex roles and the sexual division of labor
• Sexual selection theory
• Human mate preferences sexual selection

3
Sex, sexuality mating

• In sexually dimorphic species, how do biologists
  tell males from females?
• Sexual differentiation in humans
• Sex roles and the sexual division of labor
• Sexual selection theory
• Human mate preferences sexual selection

4
How do biologists tell males from females?

• Not behavioral, not chromosomes (?birds XY)
• Gamete size
• Always 2 sexes?
• Mating types
• Alternative sexualities in nature
• Hermaphrodites
• Simultaneous, sequential
• 2 different male morphs

Only they know the difference...
5
Sex, sexuality mating

• In sexually dimorphic species, how do biologists
  tell males from females?
• Sexual differentiation in humans
• Organizing activating effects of hormones
• On body and brain
• Sex roles and the sexual division of labor
• Sexual selection theory
• Human mate preferences sexual selection

6
Sexual differentiation in humans

• Women men same genes
• H-Y antigen switch, release of sex hormones
  turns genes on off
• Steroid sex hormones
• Organizing effects Permanent sexual
  differentiation of an organ
• E.g., genitals (certain circuits in brain?)
• Activating effects effects that can be reversed
  by removal of hormone
• Puberty beards, voice, breasts (mating
  psychology?)

7
All embryos start out female

• Androgens
• steroid sex hormones, secreted by testis
• turn fetus into a male
• Rabbits remove gonads, inject androgens at right
  time?genetic female turns into male
• Humans sexual differentiation starts 8 weeks
  after conception
• Distinguish from activating effects of hormones
  at puberty

8
Organizing effects of androgens

• Natural experiments
• CAH Congenital adrenal hyperplasia
• 5 alpha reductase deficiency (Dominican Republic)
• Can tell us about
• Organizing effects of androgens
• How much does socializationthe way people treat
  us as we grow upaffect
• Gender roles?
• Gender identity?

9
Organizing effects of androgens Congenital
adrenal hyperplasia (CAH)

• CAH caused when a genetic female is exposed to
  androgens early in embryonic development
• Malfunction of adrenal glands
• Dont produce cortisol
• Instead produce a hormone structurally
  functionally similar to testosterone
• Causes genital masculinization
• Enlarged clitoris fusion of labia
• Does it masculinize the brain????

10
Organizing effects of androgens Does CAH
masculinize the brain?

• 17 CAH girls After birth external genitalia
  surgically feminized given hormone treatments to
  control androgen production
• Hormones are like other girls
• Socialized like other girls
• Differ ONLY in prenatal exposure to androgens
• What happens to them?
• Androgens Organizing effect on brain?
• Can socialization over-ride organizing effects of
  prenatal androgens

11
Organizing effects of androgens Does CAH
masculinize the brain?

• 17 CAH girls vs. unaffected mothers sisters
• CAH tomboys
• More rough play, preferred boys as playmates more
  than sisters did ( more than mothers recalled
  having done)
• Fewer daydreams of wedding, marriage, pregnancy,
  motherhood
• 14/17 little or no interest in dolls (compared
  to only 1 of sisters)
• Less interest in clothes, jewelry, makeup, hair,
  babies

12
Organizing effects of androgens Does CAH
masculinize the brain?

• Yes!
• Androgens have an organizing effect on the brain
• masculinizes various programs
• Gender role socialization does not completely
  over-ride this organizing effect

13
Organizing effects of androgens 5 alpha
reductase deficiency (Dominican Republic)

• How strong are the effects of socialization on
  gender identity, compared to effects of
  hormones???
• 5-ARD XY, with enzyme deficiency, interferes
  with genital masculinization
• Study 18 boys that looked like girls at birth
• Thought to be girls at birth
• Therefore raised as girls

14
Organizing effects of androgens 5 alpha
reductase deficiency (Dominican Republic)

• Dominican Republic Sexually differentiated roles
  for children
• Girls dress differently, help mom in household
• Boys accompany men in agricultural activities
• At puberty these girls turn into boys
• Voices change, masculine musculature, external
  genitalia looks v. similar to normal males
• They undergo a spontaneous sex change at puberty!

15
Organizing effects of androgens 5 alpha
reductase deficiency (Dominican Republic)

• What happens when you are socialized as a girl,
  but hormones change you into a boy at puberty??
• Does early socialization as girls determine their
  gender identity?
• Does gender identity switch at puberty?
• Are they attracted to men or women?

16
Organizing effects of androgens 5 alpha
reductase deficiency (Dominican Republic)

• 18 5-ARD children studied
• 17 of 18 changed to male gender identity at
  puberty (1 of 17 continued to dress as woman)
• 15 of 18 married women
• Only 1 of 18 retained female identity denied
  attraction to women
• Striking apparent ease with which these men
  adapted to a spontaneous sex change, even after
  having been socialized as girls

17
Organizing effects of androgens 5 alpha
reductase deficiency (Dominican Republic)

• Striking apparent ease with which these men
  adapted to a spontaneous sex change, even after
  having been socialized as girls
• Suggests organizing effects of prenatal androgens
  on brain (? brain org.)
• Suggests heavy socialization does not over-ride
  these organizing (, at puberty, activating)
  effects

18
Sex, sexuality mating

• In sexually dimorphic species, how do biologists
  tell males from females?
• Sexual differentiation in humans
• Sex roles and the sexual division of labor
• Sexual selection theory
• Human mate preferences sexual selection

19
Sex roles the sexual division of labor

• Sexual division of labor found in every human
  culture
• But what counts as mens work vs. womens
  work differs somewhat from culture to culture
• Childcare usually falls more on women
• Sex role socialization occurs
• Question What kinds of programs accomplish sex
  role socialization?
• Ones specialized for learning gender roles?
• Or domain-general learning mechanisms?

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Sex roles the sexual division of labor What
kinds of programs accomplish sex role
socialization?

• ?? (no one asks the question!) Educated guesses?
  E.g., Are programs that cause you to learn the
  dress/ornamentation of your sex same as those
  that cause attraction to one sex or other?
• Transvestite men
• Prefer to dress in womens clothes
• Many are heterosexual
• Homosexual men Few are transvestite
• Dissociation!

21
What kinds of programs accomplish sex role
socialization?

• Are programs that cause you to learn the
  dress/ornamentation of your sex the same as those
  that cause attraction to one sex or other?
• Dissociation. Suggests programs causing sexual
  preference are different from programs that
  govern learning of gender-specific ornamentation

22
Sex, sexuality mating

• In sexually dimorphic species, how do biologists
  tell males from females?
• Sexual differentiation in humans
• Sex roles and the sexual division of labor
• Sexual selection theory
• Why is sexuality as it is in humans and different
  from other species?
• Human mate preferences sexual selection

23
When sex differences?

• Basic Principle
• In domains where ? and ? have the same adaptive
  problem to solve, expect same cognitive solution
  in both sexes
• In domains where ? and ? have different adaptive
  problems to solve, expect sexes to have evolved
  different cognitive solutions
• Mating a domain in which ? and ? mammals often
  have somewhat different adaptive problems to
  solve
• Expect some sex differences in mating psychology

24
Sexual selection

• a form of natural selection driven by
  competition for mates. In sexual selection, the
  characteristics of one sex set up selection
  pressures that affect the evol-ution of the
  design features of the other sex.
• Example the male peacocks long tail
• Can be selected for because of female
  preferences, even if these
  are initially arbitrary

How do I escape predators with this thing??
25
Runaway sexual selection

• Assume ? peacocks prefer to mate with ?s whose
  tails are slightly longer than local average
• Then ?s with slightly longer tails would attract
  more ?s, ? have more offspring
• ? ave tail length longer in next generation
• But since ?s still prefer tails slightly longer
  than average, longer tailed males will still
  attract more mates, have more offspring, so
  on...
• So properties of one sex (? preference) can
  select for a trait in the other sex (long ?
  tails) sexual selection

26
Runaway sexual selection

• ? directional selection

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Runaway sexual selection, contd

• Even if ?s initial preference arbitrary, after
  some generations, selection will favor that
  preference
• ?s who choose longer tailed ?s will have longer
  tailed sons,
• Their longer tailed sons will attract more mates
  and
• These sonswho have moms geneswill pass her
  preference for longer tails onto his offspring,
  including his daughters...etc
• Arms racecan lead to odd outcomes
• Huge tail
• But not all forms of sexual selection create an
  arms race...

28
Sexual Selection Parental Investment

• General principle
• Whichever sex invests the most in offspring
  becomes a scarce resource from the point of view
  of the other sex.
• The other sex will therefore compete for access
  to the sex that invests the most.
• Important issue
• Is the investment physiologically obligatory, or
  could it be diverted to other ends? (e.g.,
  parenting effort versus mating effort)

29
Sexual Selection Parental Investment

• Female mammals (including humans)
• Parental investment that is physiologically
  obligatory
• Internal fertilization, pregnancy, lactation
• Huge commitment of time metabolic resources in
  mammals
• Women to have an offspring, large mandatory
  initial investment

30
Sexual Selection Parental Investment

• Male mammals (including humans)
• Only mandatory investment few minutes small
  amount of sperm
• Space capsule, 10 men 1 woman, vs. 1 man 10
  women
• Other forms of investment (provisioning with
  food, protecting, etc) not physiologically
  mandatory
• Same effort/energy could be devoted to parenting
  or mating

31
In species where ?s invest more than ?s

• Reproductive rate ? investment is rate-limiting
• ? can ? his reproductive success by finding
  fertilizing many different ?s
• ?, in many species one finds ?s competing for
  sexual access to ?s, either through
• Fighting or
• Offering females gifts (or both)
• In such species ?s generally more choosy than ?s
  about who they mate with
• Given large investment, more to lose by a bad
  choice of mate

32
In species where ?s invest more in offspring than
?sWhat happens if there is nothing ? can invest
directly in a ?? (e.g., grazing mammals)

• Competition among males for sexual access selects
  for larger males with dangerous weaponry
• Larger ?likely to win fights, get sexual access
• Largers have more offspring selection for larger
  ?s
• Selects for preference for larger ?s in females
• ?s who choose larger males will have larger, more
  sexually successful sons
• Who pass on moms preference
• to their daughters
• Sea lion video

33
Sex-reversed species as an empirical test
Does which sex invests more select for
competitive choosy behaviors as predicted?

• What happens in species where ?s invest more in
  offspring than ?s?
• ? investment is rate limiting resource
• ? can ? her reproductive success by finding
  fertilizing many different ?s
• ? should see ?s competing for sexual access to ?
• Should see ?s choosy about who they mate with
• Jacana video

34
What happens when both sexes invest in offspring?

• Must form cooperative alliances
• Different selection pressures
• Both sexes choosy
• Traits conducive to cooperation important
• Albatross video
• Must trust to return with food after weeks

35
Sex, sexuality mating

• In sexually dimorphic species, how do biologists
  tell males from females?
• Sexual differentiation in humans
• Sex roles and the sexual division of labor
• Sexual selection theory
• Human mate preferences sexual selection
• Resources, fertility
• Do mens minds differ from womens?
• Sexual jealousy

36
Human mate preferences

• Both sexes invest
• Women high mandatory investment
• Men protecting provisioning
• Why do human males invest so much more than other
  male mammals do?
• Hunting meat
• Compact, easy to carry, high calorie, high
  nutrient
• Ancestral ? hunter-gatherers could compete for ?s
  by offering to invest in them their offspring

37
Human mate preferences

• Ancestral ? hunter-gatherers could compete for ?s
  by offering to
• Provision woman with food
• Provision a womans children with food
• Protect woman her children from
• Predators
• Physical aggression
• Use their own status in the social group to
  promote interests of their children

38
Sexual selection in humans

• Should favor programs that cause us to prefer
  certain kinds of mates over others
• What characteristics would sexual selection
  theory lead you to expect
• Women to look for in a husband?
• Men to look for in a wife?
• Expect mate preferences now?ones that were
  adaptive ancestrally
• Modern skulls house stone age mind

39
Human mate preferencesCross-cultural study

• David Buss, 37 cultures
• Rate how much you value each of these traits in a
  potential mate
• Any consistency across cultures?

40
Long term cooperative alliances

• For both sexes same problem, same solution
• Value traits indicating a competent reliable
  cooperator
• Most highly valued traits by both sexes
• kind and understanding
• intelligent
• Cultures differed only in which order

41
Adaptive problems that differ?different
preferences in men women

• Hunter-gatherer women
• Do better with man willing and able to invest in
  her and her offspring
• Provision with resources
• Protect
• Especially 1st 18 months, 3 years
• Hunting, protecting more variance in ability
  than for gathering

42
Womens mate preferencesPrediction sex
difference in valuing of ability to provide
resources

• Potential mates ability to provision women
  should value this more than men
• Earning capacity
• Status
• Men dont care about womens status
• Women prefer high status men
• Townsend study biz suits vs. burger king
  uniform, statements of ambition

43
Womens mate preferencesPrediction sex
difference in valuing of ability to protect

• Ability to protect?
• Willingness to defend?
• untested

44

• Women Which do you find most attractive?
• Men Which do you think women find most
  attractive?
• B average of 117 male faces (average is
  attractive hypothesis)
• A Feminized warped 20 toward ? (UK prefered)
• CD warped 20 50 toward highly masculinized
  face (US D prefered)

45
Mens mate preferencesPaternity certainty
Adaptive problem diff.

• Maternity certain (Who came out of my body?)
• What about paternity??
• Men at risk of investing in child not their own
• Solution Value sexual fidelity
• What counts? Compare to local average
• If womans children fathered by multiple
  men?divide resources among children
• Solution monopolize womans entire reproductive
  career. Value youth.
• Peak reproductive value versus peak fertility

46
Mens mate preferencesPaternity certainty
Adaptive problem diff.

• Reproductive value
• How much of reproductive career in front of you?
  Peak right after menarche 15-18 years
• Fertility
• When most likely to conceive? Peaks 23
• Prediction about sexual attractiveness
• Which most attractive as a long-term mate?
• For brief fling?

47
Mens mate preferencesFemale fertility Adaptive
problem differs

• Men stay fertile, gently declines with age
• Women declines fast
• Marital rates

48
Mens mate preferencesFemale fertility Adaptive
problem differs

• Problem need young (fertile) ?, but age not
  known
• Solution Find cues correlated with youth/ health
  sexually attractive
• Skin quality, absence of disease, high energy,
  firm breasts (no evidence of nursing)
• Define what counts as attractive
• 100 of Busss 37 cultures men valued youth
  attractiveness women did
• Sex diff Moderated by disease load!

49
Female attractiveness What counts?

• Arbitrary standards of beauty?
• Risk of famine? ? plumpness valued when no
  famine risk
• What about the face?
• Any invariants across cultures?
• Principled differences?

50
What about the face?

• Don Symons When tails of distribution bad,
  prefer average

Mathematically average face attractive
51
Facial beauty across cultures

• What happens if mathematical average is prefered?
• Same averaging mech? Different standards of
  beauty in different cultures!
• Is average the only thing?

52
B
A
C

• Which is most attractive?
• A average
• B average from top 25 in attractiveness
• 90 prefer B over A
• C caricature of B, exaggerating where B
  differed from average by 50
• 70 prefer C over B

53
What counts as attractive?Any other invariants?
54
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55
Waist-Hip Ratio

• Differ on WHR weight
• Preference for .7-.8 WHR
• Preferred weight? Cross-cultural differences

56
Waist-Hip Ratio (WHR) tracks female fertility
parity

• Before puberty 1
• After puberty
• Pregnant 1
• ? w/ children born Menopause 1
• WHR tracks age-related fertility
• WHR tracks pregnancy status
• WHR related to optimal hormone profile
• Hips made of brain-building fat!
• Centerfolds plumpness differs, not WHR

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58
Different preferences in men women Caused by
different programs?

• Structural powerlessness claim No
• Same mate choice programs
• Different environments
• access to resources ? women must choose men with resources men can
  choose women regardless of resources
• Why WHR, young, etc?

59
Different preferences in men women Caused by
different programs?

• Structural powerlessness predicts
• As women gain more power resources, their
  preferences should become more like mens
• Care less about mans resources status
• (Presumably prefer young to older men)
• Results famous feminists, medical law students

60
Different preferences in men women Caused by
different programs?

• Results famous feminists, medical law students
• ?status/ resources ? wanted even ?status/
  resources in a ?
• Wanted men with wealth/status own
• Opposite of structural powerless prediction!
• Makes sense if
• People with more power can enforce higher
  standards
• Womens standards are just different from mens

61
Sexual fidelity both sexes should care

• Sexual jealousy
• All cultures
• Infidelity or accusation of infidelity Leading
  cause of spousal homicide
• Different risks
• Men wife gets pregnant by someone else, he
  invests in another mans child
• Threat sex with another man
• Women husband diverts investment to another
  woman her children
• Threat emotional attachment to another woman

62
Sexual jealousy Sex difference in triggers?

• Sexual versus emotional infidelity (Buss)
• What would upset you more (a) imagining your
  mate having sexual intercourse with someone else,
  or (b) imagining your mate forming a deep
  emotional attachment to someone else?
• American women 85 emotional
• American men 60 sex
• Committed relationship more said sex
• Other cultures different absolute levels, but
  men always dislike sexual more than women