problems of parenting - department of psychology ...psy.cmu.edu/~rakison/chapter7outline.pdf ·...
TRANSCRIPT
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Problems of Parenting
Dawkins: Family Planning
Optimal Clutch Size
a. costs of producing too many offspring
1. food spread too thin
2. parenting spread too thin
b. adaptations that limit offspring production:
evolve NOT for benefits of the group, rather
FOR benefit of mother (i.e., genes of the mother)
in maximizing number of surviving children
Conclusions on Family Planning
Genes for having too many children are NOT passed on to next generation, since fewer of the children bearing these genes reach adulthood.
Therefore: Adaptations to produce optimal number of offspring, NOT maximum number of offspring.
Dawkins: Battle of Generations
Parental Investment: Investment
that increases one offspring’s RS
at cost of parent’s ability to invest
elsewhere.
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Should parents invest more
in older child?
a. more costly to get younger one up to
reproductive age
b. but . . . units of PI more beneficial to
younger one
Why do mothers
provide more parental care
than fathers?
The paternity uncertainty
hypothesis
Mothers are 100% “sure” of genetic contribution to offspring
Strongest in species with internal fertilization
Makes parental investment less profitable for fathers than mothers
Mating opportunity cost hypothesis
Higher for males than females
Parental effort versus mating effort– men benefit more from securing
additional mates
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Mating Opportunity Cost
Hypothesis May Explain Individual
Differences Among Men in
Parenting
When surplus of men, men have trouble pursuing ST mating
Men attractive as ST mates predicted to do less parenting.
Population density should lower men’s parenting effort due to more ST mating opportunities
Conclusions about Why Mothers
Invest More than Fathers
Paternity uncertain hypothesis and mating
opportunity cost hypothesis are both
promising.
What are parenting adaptations
sensitive to, theoretically?
Genetic relatedness of
offspring
Ability of offspring to convert
parental care into fitness
Alternative uses of the
resources
Issue #1
Genetic relatedness to child.
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Parents’ investment in children
Different levels of
fathers’ investment in
college education,
depending on:
– Genetic relatedness
– Paternity certainty
– Children of current or
former mate
Two ways of assessing paternity
Partner’s sexual fidelity during the period in which she conceived
Perceptions of the child’s resemblance to him
– Mother’s comments after childbirth
– Relative’s reports of resemblance
Martin Sheen – Apocalypse Now
Charlie Sheen – Platoon
Empirical Evidence
fMRI study: more cortical activation when men look at images of children whose faces resemble their own.
Men whose children look more like them invest more time and attention.
Men who perceive that their wives are loyal and trustworthy invest more in kids.
Sex Differences in Parenting
Women spend more time than men looking at images of infants.
Women are more skilled than men at recognizing emotional expressions of infants
Women are more likely to tend to infants—a cross-cultural universal
Women are more likely to “befriend” others for the goal of helping to protect their infants
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Child abuse and other risks of not
living with both parents
1. Children living with one genetic and one step-parent are roughly 40 times more likely to be physically abused
– "Step-parenthood per se remains the single most powerful risk factor for child abuse that has yet been identified." --Daly & Wilson (1988)
Child abuse risks of not living with
both parents
Child homicide as a function of
genetic relatedness to offspring
Child Murder More Common by
Step Parents
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Thought Experiment
Why do stepparents abuse and kill
stepchildren so much more often than
genetically related children?
Infanticide in Lions
Two Hypotheses About Step-
parental Abuse
1. Byproduct hypothesis: Abuse as byproduct of failure of stepchildren to “engage” the normal psychological mechanisms of parental love (Daly & Wilson).
2. Adaptation hypothesis: Adaptations to inflict costs on, or eliminate, unrelated cost-absorbing kids (Buss & Duntley)
Issue #2
Offspring’s ability to convert parental care
into reproductive success
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Evidence
1. parental neglect and abuse of children
with congenital abnormalities
2. greater maternal care of healthier twin
3. young kids, who are therefore less
reproductively valuable, are killed more
Parental neglect and abuse of children
with congenital abnormalities
12% (16,000) of institutionalized children are never visited
22% (30,000) are visited once a year
As many as 60% of children with congenital abnormalities who live at home are abused
Maternal care based on the health
of the child
Study of maternal behavior
toward twins
– At 4 months, mothers
directed same amount of
positive behavior toward
both twins
– At 8 months, mother
directed more positive
behavior toward healthier
twin with no reversals
Age of child and risk of
infanticide
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Thought Experiment
Why do mothers kill young infants?
Two Competing Hypotheses
Byproduct hypothesis: Because parents feel more love for kids better able to convert parental care into RS, and less love to others, killing is a rare and extreme byproduct of lack of love (Daly & Wilson)
Adaptation hypothesis: Mothers have adaptations to kill infants who are deformed, etc. (Buss & Duntley)
Issue #3
Alternative uses of parental resources.
Age of mother and infanticide
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Women’s marital status and
infanticide
Puzzling Cases of Mothers Who
Kill Children
Parental Effort v. Mating Effort
1. fathers spend less time with kids than mothers, even among the Aka tribe.
2. Women have greater pupillary dilation to pictures of infants [a measure of interest]
Women can read infant facial expressions more accurately and quickly than men.
Conclusions
Young unwed mothers who lack an
investing father are far more likely to kill
infants.
Byproduct or adaptation? -- need
evidence of special design.
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The Trivers-Willard Hypothesis
"In species with a long period of parental investment after birth of young, one might expect biases in parental behavior toward offspring of different sex, according to the parental condition; parents in better condition would be expected to show a bias toward male offspring."
Trivers, R.L., and Willard, D.E., 1973.
Trivers’s Theory of Parent-
Offspring Conflict
Parent-Offspring Conflict
Mother-offspring conflict in utero
Mother and fruit example of diminishing returns
Predictions of parent-offspring conflict
– parents and children will get into conflict about the time the child should be weaned
– parents will encourage children to value their siblings more than they are naturally inclined to do
Mother-Offspring Conflict In Utero
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Oedipal Complex
Freud and his mother
Class Thought Experiment
Would you let you parents choose
your LT mate?
Conflict over mating
Offspring value beauty more than parents:
parents value family background
Conflict over short-term strategies,
particularly for daughters
Conflict over parents choosing a new
mate
Homicide Data
Homicide as assay of conflict: logic of (tip
of iceberg)
No evidence of same-sex contingency
during preschool years
– 21 boys killed by father, 21 boys killed by
mother
– 27 girls killed by father, 27 girls killed by
mother
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Adulthood: evidence of same-sex
contingency
– 60% male-male familial homicides (father or
son victim)
– 27% male killer, female victim
– 5% female killer, male victim
– 9% female killer, female victim
d. In sum: adulthood same-sex contingency
in familial homicides, but this is a decade
after end of Oedipal stage.
Asymmetry of Valuing Parents
and Children
Asymmetry of Valuing Parents
and Children
Genetic r = .50 between parents and children
It does not follow that they value each other
equally
As parents age, they become less and less
valuable to kids
Simultaneously, kids become more valuable to
parents, as other avenues for parent’s fitness
diminish.
Asymmetry of Valuing Parents and
Children, continued…
Prediction: Those less valuable are at more
risk of getting killed
82% of father-son homicides were son killing
father v. 18% father kill son
Perhaps explains why your parents want to see
you more than you see them!
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