Download Evolutionary Psychology

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Evolutionary Psychology
Background
Assumptions
Criticisms
Areas
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Violence
Altruism
Mating strategies
Mental modules
The Science Background
• Biology
– Darwin great observer
– Exposure to new areas
• Geologists stretching time
• Previous evolutionary theories
• Hobbes
The Philosophical background
– View of human nature
– Hobbesian problem of order
• Malthus
– Struggle for existence
• Alternative views
– Cambridge Platonists
– Moral sentiments
• Basis
Darwin’s theory -- competition
– For food & shelter
– Protection for predators
– Con-specifics
• Features which allow survival will allow individual to live long enough to breed
– If genetic be passed along
– Darwin unclear how these genetic changes took place
Darwin’s theory – sexual selection
• Typically females pick mate
• Strength or other physical features
• Sometimes display
Darwin’s Theory III
• Criterion for biological success
• Passing along own genes
Early misuses
• Social Darwinism
• Reliance on empty instincts
Modern additions
• Hamilton’s notions of inclusive fitness
– The problem of altruism
– Keeping genes alive through benefiting kin
• Now what is being selected is genes and not individuals
– People are then mere vehicles for carrying and protecting genes
Evolutionary psychology
• Not much interest in obviously adaptive features
– Intelligence
– Physical abilities
• Four main areas of concern
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All related
Mental modules
Social relationships
Violence
Mating strategies
Evolutionary Psychology assumptions
• That human features evolve in response to environmental pressures
– Physical features
– Abilities and capabilities
– Motivations or propensities to action
• Environmental features construed broadly
– Physical environment
– Other animals
– Other humans (con-specifics)
Evolution with respect to particular environments
• Ground squirrels
– Females mate with many males
– So many litter mates are half- siblings
– Territorial aggression much more common among half sibs than full sibs – solves an
environmental problem
• Humans?
– MZ twins less likely to be aggressive?
– No reason for this strategy to evolved because such twins are rare and not likely to have
survived
– Competition among successive sibs of different fathers might be selected for
Evidence for evolutionary psychology
• Human universality
• Continuities with other animals
– Data from their behavior
– Similar environmental pressures
• Often in far past
– Genetic continuities
• Genetic information
• Experimental data
Criticisms – as science
• Telling stories and metaphors
– But lots of science relies on metaphor and narrative
• Failures to outline mechanism
• Sprandals – Gould
Criticisms – Biological determinism I
• Previously argued that true only if all scientific explanations implicate determinism
• Levels of analysis
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Not a theory of motivation
Propensity to certain mate selection strategies does not mean determined
Anymore than needing food for survival means we consciously eat to survive
What genes “want” and what I want are often different
Criticisms – Biological determinism II
• Many causes of any given behavior
– Some may be evolutionarily significant
– Others may not
• We often do things for cultural or idiosyncratic reasons
– May have evolutionary basis
– Or not
Criticisms -- political
• Echoes of Social Darwinism
– Promotes superiority of some groups
– Racism
– Sexism
• Problems with this
– Not necessarily true – a misunderstanding of the model
– And applies equally strongly to environmental explanations – Nazi vs Marxist
• Hume and Moore
The Naturalistic fallacy
• Can’t derive an “ought” from an “is”
• Our values and moral often trump biological dispositions
– May have evolutionary significance
– May not
Evolutionary account of social behavior
• Have to account for conflict and violence
• And also for pro-social behavior and altruism
• But to some extent these may be part of the same package
Hobbes on violence
• “So that in the nature of man, we find three principal causes of quarrel. First,
competition; secondly diffidence; thirdly, glory. The first maketh man invade for
gain, the second for safety, the third for reputation. The first use violence to make
themselves masters of other men’s persons, wives, children and cattle, the second to
defend them; the third for trifles, as a word, a smile, a different opinion, and any
other sign of undervalue…”
Consider first violence
• Competition among con-specifics is “natural”
– Food and other resources
– Breeding privileges
• Competition is necessary evolutionarily
– Weeds out weak and less competent
– Promotes genetic diversity
Is competition the same as violence
• Passive competition
– All plants and animals
– Examples
• Better access to food
• Run faster so colleagues get eaten
• Violence facilitated by competition
– Fighting over food resources
– Fighting over breeding privileges
Main concern is emotional violence
• Considerable evidence that this too is “in the genes”
• The main evidence is the association of violence with gender
– In all cultures men commit at least 85% and usually more like 95% of all violence
– And in all cultures this has the same pattern
Male violence patterns
• Males mostly kill males (UCR, 1976-2002)
Victims of Male Violence
• Male victims
– Robbery related
– Insults and threats
• Female victims
– Most romantic relationships
– And fueled by jealousy
Victims of female violence
• Children
• Spouses and lovers
• Almost never strangers or robbery related
The evolutionary program
• Roughly people are programmed to ensure that their genes are passed
along
• Should therefore be less likely to kill those with genetic overlap
• And be more likely to kill those who use resources but do not share genes
Evidence from murder statistics
• Children under the age of 5
– 31% killed by fathers
– 30% killed by mothers
– 23% killed by male acquaintances – usually boyfriends of mother
• Within families men much more likely to kill stepchildren – stepchildren about 70
times more likely to be killed
• Children are 100 times more likely to be abused when living with a step parent
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When mothers murder children
More common with twins
More common when older children
More common with unhealthy or deformed
More common with female children
More common with lack of parental or spousal support
More common with younger mothers
Explaining male violence
• Fueled by sexual competition
• Across species related to sex fitness variance differences
– Fitness variance refers to the variability of children produced.
– In most human societies the variance is much larger for males than for females
• Also related to size differences between males and females
Sex Fitness Variance
• Males can produce many more children than females
• Variance of number of children per male
– Some males have many
– And many have none
• Variance of number of children per female
– Typically much lower
High male / female ratios
• Must mean that some males have multiple and many sexual partners while others
have none
• Effectively polygamous
• And would promote male competition over sex with females
• Other features
– Males larger than females
– Male die sooner, often because of risky behavior
Competition for reproduction
• Thus males need to compete for breeding partners
• Shows of strength are important
– Females prefer stronger males
– Stronger males beat up weaker ones
• Thus violence (or threats) is a kind of display used to acquire breeding partners
• Also males more possessive of females
– Fear of caring for child of another
– Opportunities for sex
Translations into human violence
• Males should kills sexual partners more from jealousy
– They do
– And more likely to treat women as property
– Females more likely to kill partners because of abuse
• Males should kill stepchildren more often – they do
• Males should more often kill because their status has been threatened
• Males more likely to kill to acquire property to impress females
Mating strategies
• The centerpiece of evolutionary approaches
• Affects directly likelihood of genes being passed on
• Generally but not inevitably different for males and females
– Varies by species
– And environmental pressures
Male strategies
• Should prefer multiple partners
• And little responsibility in rearing
• Prefer fertile sexual partners
– Young
– Attractive – healthy
• Symmetrical bodies and faces
– Correlated with health
– And with attractiveness
• Other signs of health
– Hip-to-waist ratio
Female strategies
• Should prefer protective males
• And males that are reliable
• Cues
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Maturity
Masculine features – related to testosterone
Resources
Body tone – not necessarily highly muscular
• Marriage patterns
Supportive evidence
– Males marry younger women
– Women marry richer men
– Attractive people more likely to get married
• Reported preferences
– Men rank physical attractiveness higher
– And women rank resources
• Personals ads
• Males
The jealousy issue
– Want to be sure children are theirs
– Hence jealousy of sexual infidelity
• Women
– Want to be sure male mate is reliable and committed
– Hence more jealous of intimacy infidelity
Group behavior and altruism
• Key issue not resolved by Darwin
– How could altruism be established given that altruists often die
– Only arises for social species
• Important, obviously, as inhibition on violence
Types of altruism
• Kin based
– Hamilton’s notion of inclusive fitness
– Helping kin allows own gene’s to survive even if altruist dies
• Help should be in proportion to genetic relationship, and in most species it is
• Reciprocal
– Helping non-kin
– Essential in social groups – cannot survive without it
Reciprocal altruism
• Helping others in expectation of being helped in return
• The “free-rider” problem
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Major adaptive problem of group living
If free-riders are undetected they will tend to survive longer
And their genes come to dominate
With altruism thus dying out
Solving the free-rider problem
• Necessary features
– Detect cheating
– Recognize individuals and remember who has cheated
– Refusing to help those who cheat
• Corollary mental development
– Moral emotions
– Theory of mind
Moral emotions – efficient control
• Other condemning – punish cheaters
– Anger
– Contempt
• Other praising – reward people who do not cheat
– Gratitude
• Other suffering – sympathy with needy
– Empathy
– Compassion
• Self-conscious – inhibit cheating
– Shame
– Guilt
Theory of Mind
• Larger groups require more indirect solutions
• Language helps – shared reputations
• Theory of mind
– The notion that beliefs and desires control behavior
– Understanding the behavior of others in terms of inferred beliefs and desires
Development of theory of mind
• Children have by 4 or so
• Autistics do not have
• False-belief test
Mental modules
• Argument that the mind cannot have evolved as a general problem solver
• The environmental challenges are too varied
– Issues confronting a visual system are not the same as those confronting an
auditory one
– And neither has much to do with logical analysis
The source of modules
• Demands of physical environments
• Demand of social environments
– Likely to have some role on language development
– Morality
– Cheating detection
Borrowing
• Various cognitive capacities need not have been selected for directly
• Deduction may be a by-product of cheating detection
• We do not necessarily parse behavior and abilities the same way nature
does
• Hotly debated
What are the modules
– Some claim many, perhaps thousands
– Other claim a very few
• Some agreement on
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Language
Mathematics
Naive physics
Naïve biology
Perhaps naïve psychology
Effectiveness of modules
• Evolved many 1000 years ago and in different circumstances
• In more complex world today may lead to errors