Transcript What about sexual behavior? - The Home for NDEC Students

What Motivates Us: Sex
INTRO TO PSYCH
4/10/14
Sex
 People say sex is their favorite activity
 They rate it higher than sports, hugging and kissing, eating,
going on trips, shopping, etc
 The average American devotes 4 minutes and 3
seconds to sex (per day)
 What does this tell us?
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1) People don’t actually spend that much time on sex
2) Regardless of how much time we spend on sex, it’s hugely
important in our lives
Everything follows from it: marriage, family, children, some
aggression, competition, art & music
 If we were a creature without sex, everything would be different
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Sex
 The very existence of sex is a mystery
 Many animals have just one sex, and reproduce by cloning
 But complex animals (like humans) have two sexes
 To reproduce, each animal gives half its genes to its
offspring
 It’s a puzzle how multiple sexes ever evolved
What are we going to talk about?
 How and why males and females are different
 What people find sexually attractive
 What are the origins of sexual preference?
 Sex is difficult to talk about
 Very emotional and intimate part of life
 Lots of moral implications & consequences
Morality & Inevitability on Evolution, Sex &
Gender
 Biologists argue that sexual behavior, action, &
desire are a biological adaptation that exists for us to
be able to spread our genes
 By this definition, non-procreative sex does not serve
the reproductive goal and may be considered
unnatural – Does this mean it’s wrong??
 If sex for reproduction has evolved out of natural
selection, does this make it good/moral/inevitable?
Morality & Inevitability on Evolution, Sex &
Gender
“Nature does not dictate what we should accept or
how we should live our lives. Well into my
procreating years, I am so far voluntarily childless,
having squandered my biological resources reading
and writing, doing research, helping friends and
students, and jogging in circles — ignoring the solemn
imperative to spread my genes. By Darwinian
standards, I am a horrible mistake, a pathetic loser,
but I am happy to be that way, and if my genes don't
like it they can go jump in the lake.” – Steve Pinker
Morality & Inevitability on Evolution, Sex &
Gender
 What is the point of this quote?
 Certain things we do exist to serve natural selection
 But that doesn’t make them right
 If you think that something is only right if it leads to
reproduction, then you’re probably not going to think
very much about birth control
 If you think something is wrong if it’s unnatural, then
you’ve got some strong beliefs on flying in a plane, or
refrigerating your food, or surviving a severe infection
Morality & Inevitability on Evolution, Sex &
Gender
 Our bodies & brains have evolved for reproductive
success
 But we also use our brains to choose our own
destinies
 Keep morality in mind as we discuss different claims
about what has evolved & what hasn’t
 But what about inevitability?
Morality & Inevitability on Evolution, Sex &
Gender
 “If a child has had bad teaching in mathematics, it is
accepted that a resulting deficiency can be remedied by
extra-good teaching in the following year. But any
suggestion that the child's deficiency might have a
genetic origin is likely to be greeted with something
approaching despair. If it's in the genes, it is determined
and nothing can be done about it. This is pernicious
nonsense on an almost astrological scale. Genetic causes
and environmental causes are in principle no different
from each other. Some may be harder to reverse, others
may be easy. What did genes do to deserve their sinister,
juggernaut-like reputation? Why are genes thought to
be so much more fixed and inescapable in their effects
than television or books?” – Richard Dawkins
Morality & Inevitability on Evolution, Sex &
Gender
 The point: What causes something to be is logically
separate from what can reverse it
 Genetics that can be reversed
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Example: My bad eyesight
It’s bad because of my genes; my mom’s side has terrible eyesight
 But it’s easy to fix – glasses and contact lenses
 Biologically caused but easy to fix
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 Cultural and hard to reverse
 Example: the way society treats obese people
How thin or how fat you think someone is is not genetic
 It varies a lot from culture to culture
 But once it is part of the culture, it’s very hard to get rid of
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Basic Sex Ed
 What’s the difference between male & female?
 Penis & vagina?
 Nope – there are some animals that have neither one
 Definitions:
 Male: possess a small sex cell that carries genes and nothing
else (sperm cells)
 Female: possess a big sex cell that carries genes and food and
has a protective covering (egg)
Basic Sex Ed
 Why is it that the animal with the tiny sex cell is
typically larger and more aggressive than the animal
with the larger sex cell?
Basic Sex Ed
 “Parental Investment”: Any investment that will
increase an offspring’s chance of survival at the cost
of the parent’s ability to invest in other offspring
 Typically with mammals, females have a much
higher parental investment
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Female Parental Investment: carries a fetus inside her,
nourishes it with her blood (for many months), nurses and
protects it until it has grown big enough to fend for itself (for
years)
Male Parental Investment: a few minutes of copulation and a
tiny sperm cell
Basic Sex Ed
 This leads to the evolution of different psychologies
in males and females
 Males:
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A single male can fertilize several females, which forces some
males to go mateless
Those who mate with as many females as possible will have the
most reproductive success, and the genes that allow them to do
so will be passed on to future generations
 Females:
 Females can always find mates, so numbers don’t matter
 Those who mate with the right males, those whose offspring
have the best chance of surviving, will have the most
reproductive success
Basic Sex Ed
 The competition to find the RIGHT mate explains
the size puzzle
 Males are typically larger because they have to
compete with other males to mate with a certain
female
 Females are choosy! Only the best mate for me!
 Males have to compete to woo the female so, often,
males evolve special displays which exist only to be
beautiful and to be attractive to and attract mates
Basic Sex Ed
http://www.arkive.org/superb-bird-ofparadise/lophorina-superba/video-99a.html
Basic Sex Ed
Summary of the evolution of sex differences
Differences in Sex Cells
Differences in Parental Investment
Differences in the sorts of physiological &
psychological mechanisms that evolve
Basic Sex Ed
 Sometimes, parental involvement is reversed
 Males are heavily invested, females not so much
 Example: Pipefish
The male takes the eggs from the female and puts them in a pouch
that plugs in to his bloodstram
 Then the female takes off
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In cases like this, the females are often bigger and more
aggressive than the males and they compete for the attention
of the males
Penguins!
Both male and female have equal parental involvement
 Both have to take care of the egg
 Because they’re equally involved, penguins are usually the same
size
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Sex Differences Among Humans
 How we mate
 Polygamous as a species
 “Serial monogamy” as a culture
 The average human male is 15% bigger than the
average human female
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This suggest there has been male to male competition in our
evolutionary history
Which suggests there is unequal parental investment
 Males are generally meaner (physically violent)
 In utero, as children, as adults
Sex Differences Among Humans
 Sexual Choosiness
 Do males and females differ in the extent to which
they will favor anonymous sex?
 Parental Investment tells us that males should be
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It might result in impregnation and the spreading of genes
Doesn’t carry the same level of investment required for a
female
 Females have to be picky about who they mate with
Important to remember these systems evolved before
birth control & vasectomies existed
Sex Differences Among Humans
 Sexual Choosiness
 Prostitution – almost universally a male interest
 Porn – human universal
 Preference for sexual variety
The Coolidge Effect
 President & Mrs. Coolidge are being shown around a farm
 The farm guy points out all of the hens to Mrs. Coolidge
 She wonders why only one rooster? Is that enough?
 The farm guy says the rooster has sex “dozens of times each day”
 She says “Tell that to the President”
 So he does. The President asks if the rooster has sex with the same
hen every time
 He doesn’t. It’s a different hen each time.
 “Tell that to Mrs. Coolidge”
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Sex Differences Among Humans
 What does The Coolidge Effect tell us?
 Males mated with a female become uninterested in
further copulation
 But if a new female is available the male becomes
interested in copulation again
Sex Differences Among Humans
 How do we find out which males are likely to fall
under The Coolidge Effect?
 Direct Measures
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Surveys
Ask questions like “How many sexual partners would you like
to have in …the next month/the next 2 years/your lifetime?”
Men answer 2/8/18
 Women answer <1/1/4-5
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Experiments
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A very attractive man & very attractive woman approach people on
a college campus (they’re actors, not people from campus, so no
one knows them)
Sex Differences Among Humans
 These attractive actors say “I’ve been noticing you
around campus. I find you very attractive. Would you
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Go out with me tonight?
Come over to my apartment tonight?
Go to bed with me tonight?
 Over ½ the women approached say Yes I’ll go out
with you tonight
 Very few women agree to coming over
 No women agree to going to bed together
Sex Differences Among Humans
Sex Differences Among Humans
 Men:
 50% say yes to going out tonight
 69% agree to coming over
 75% agree to go to bed together
Of those men who say “no” to going to bed, 25% apologize
profusely and give an excuse as to why
 “My fiancé is in town somethingsomethingsomething”
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Sex Differences Among Humans
 What about sexual behavior?
 Difficult to figure out by studying heterosexual sex
 Men & women have different priorities for sex, which
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dictate their behavior
Homosexual sex happens purely out of sexual desire and
is better to study to determine sexual behavior
Lesbians tend to be much more monogamous than gay
men
Before AIDS, studies found gay men to be very
promiscuous (often hundreds or thousands of partners)
Women don’t have this level of promiscuity
Sex Differences Among Humans
 Gay men are doing exactly what the average
heterosexual man would do if he had that many
willing females to choose from
Sex Differences Among Humans
 What about sexual attractiveness?
 People are asked “Who do you want to be
with/marry/have as a partner?”
 Females & Males: kindness and intelligence
 Females
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More focus on power and status
High interest in investing in children
 Males
 More focus on the ability to have children
Beauty
 Beauty signals 2 things
 Youth
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Not preschool youth, sexually mature but also young
Health
Beauty Universals
 Beauty = Youth
 Large eyes
 Full lips
 Smooth, tight skin
 Beauty = Health
 Absences of deformities
 Clear eyes
 Unblemished skin
 Intact teeth
 Average face
Social Factors for Sex Differences
 Some sex differences related to aggression and mate
preference are universal across humans, show up in
other mammals, and follow evolutionary theory
 These differences are likely innate in us
 Other sex differences have origins that are less clear
 Nature vs Nurture Sex Differences
Social Factors for Sex Differences
 Babies are treated differently depending on the
gender they are
 So are we as adults
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Studies have shown that when an email or job application are
sent in, it matters whether the name on it is John Smith or
Joan Smith
 People have different expectations and different
reactions to males vs females
 Some of you may have experienced this if you have a
name that could be taken as name of the opposite
gender
Social Factors for Sex Differences
 Gender self-segregation
 Males segregate with other males
 Females segregate with other females
 This happens from age 6 – 12 (Middle Childhood!)
 All boy groups may enhance and exaggerate a boy’s
natural aggressiveness
 All girls groups may enhance and exaggerate a girl’s
natural non-aggressive behavior
Social Factors for Sex Differences
 Sex differences in empathy
 Men are more violent (includes murder)
 More testosterone in your body may make you less
social
 Boys are less empathetic than girls
 Problems with empathy, with social cognition, are
much more frequent in men than in women
Social Factors for Sex Differences
 Autism, Asperger’s Syndrome, conduct disorders,
and psychopathy are predominately male
 Some think there are also sex differences in the
capacity to be able to do math and science
 Larry Summers, former President of Harvard
 Gave a speech saying there are “issues of aptitude” in
women and that’s why there aren’t many women in
the science and math fields
Sexual Orientation
 A large majority of men are sexually attracted to women
 A large majority of women are sexually attracted to men
 A minority of the population is homosexual – Why?
 No one knows
 Overall, people do not choose their sexual orientation
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People who are gay are often discriminated against (sometimes
extremely)
Some have no wish to be gay or may even think it’s morally wrong
 This makes it implausible that their sexual orientation is
a conscious choice
Sexual Orientation
 Some studies have shown that gay and straight
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individuals are different in their sexual and romantic
fantasies before they hit puberty
Is being gay built in? Sort of
When you look between identical, fraternal, and adopted
siblings, then yes, there is a genetic predisposition to
homosexuality
But it can’t be all genetic
If I’m a gay identical twin, the odds that my twin is also
gay are 50%
If it was TRULY genetic, the odds would be 100% since
we’re clones
Sexual Orientation
 Homosexuality is an evolutionary mystery
 It doesn’t seem to follow biological adaptation
because it does not result in reproduction
 According to evolutionary adaptation view, the genes
that carry homosexuality would have been weeded
out by now
 Those carrying those genes wouldn’t have had
offspring and the genes would have died with them
 And that’s why the nature vs nurture argument to
homosexuality is such a puzzle