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Chapter 7

Evolutionary Psychology - Chapter 7 Textbook Notes

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York University
PSYC 3420
Irwin Silverman

EVOLUTIONRY PSYCHOLOGY – FINAL EXAM NOTES. CHAPTER 7: Problems of Parenting • Evolutionary perspective = offspring as a means of gene advancement for parents. • Many species do not engage in parental care at all due to the costs – therefore, in nature the reproductive benefits must outweigh the costs. - There are many adaptations of parental care found in species such as: Mexican free- tailed bats (sacrifice mental and physical state to feed pups) and nesting birds (remove shells of babies to prevent predation). WHY DO MOTHERS PROVIDE MORE PARENTAL CARE THAN FATHERS? • In both animal and human kind, females are far more likely to care for their offspring than males. - hypotheses to explain this phenomenon are: (1) Paternity Uncertainty Hypothesis (2) Mating Opportunity Costs Hypothesis (1) The Paternity Uncertainty Hypothesis: - from the males perspective, there can always be some probability that another male has fertilized the female’s eggs – therefore no passing on of their genetics. - females are 100% sure their genes get passed on because they are physically giving birth. - strongest in species with internal female fertilization: insects, humans, primates and mammals. - can explain one viable cause as to why females invest more into offspring opposed to males. (2) The Mating Opportunity Hypothesis: - are missed additional matings as a direct result of effort devoted to offspring, and is suffered by males and females. (f: breastfeeding, m: fighting off preds). - higher mating costs for males opposed to females, therefore spend less time with offspring to better their chances. - when males don’t suffer mating opportunity costs as a consequence of investing time into offspring = ripe time for evolution of male parental care. - this hypothesis may partly explain individual differences among humans. - surplus of men = invest time into children - surplus of women = negligence of children - 2 factors explain individual differences in amount of parenting: (1) attractiveness of the male as a short term mate (more attractive = reduced parental effort and increased mating effort) (2) population density (large cities = more opportunities to interact with females, rural areas = low density). AN EVOLUTIONARY PERSPECTIVE ON PARENTAL CARE • Selection will favor adaptations for parental care that have the effect of increasing the fitness of the parent. • Parental Care: the preferential allocation of investment to one or more offspring at the expense of other forms of allocating investment. • Parental Favoritism: parents favor offspring who are likely to provide a higher reproductive return on the investment. • Evolved mechanisms of parental care should be sensitive to 3 contexts: (1) Genetic relatedness of offspring: are the children really my own? (2) Ability of the offspring to covert parental care into fitness: Will my investment make a difference to the survival and reproduction of my children? (3) Alternative uses of the resources that might be available to invest in offspring: Will a given unit of my investment be best spent investing in children or in other activities such as investing in my sister’s children or in additional mating opportunities? Genetic Relatedness to Offspring • Darwinian view: substitute parents care less for children opposed to natural parents, with the result being that the children reared by people other than their natural parents will be at risk. • Parental love and resources are substantially less likely to be directed toward children by stepparents than by genetic parents. • A man has at least 2 sources of info to consider the likelihood that he is the genetic father of a given child: (1) info about his partner’s sexual fidelity during the period in which she conceived. (2) perceptions of the child’s resemblance to him. Who Are Newborn Babies Said to Resemble? • Mothers are motivated to promote a father’s certainty through the remarks of the new born baby’s resemblance in appearance to him. • Hypothesis: mothers and their kin attempt to influence the putative father’s perceptions of his paternity, presumably to encourage male parental investment in the child. (1) mothers are more likely to point out resemblances between their newborns and the father than to themselves. (2) they are more likely to comment on this resemblance when the father was present in the room than any other time. (3) when judges were asked the resemblance – more picked the mother over the father. • Men whom had offspring that didn’t look like them = more severe physical harm on their partners. Parent’s Investment in Children • Being genetically related to the child = more of an investment made in them. • More certainty of genetic relatedness = more of an investment made in them. • Men invest more in stepchild rather than natural child as a form of “mating effort” rather than strictly a “parental effort”. Child Abuse and Other Risks of Not Living with Both Parents • According to the Inclusive Fitness Theory: The less genetically related the adult was to the child, the higher the probability of infanticide. • High rates of abuse in low income families and stepfamilies. • Stepparents are at a high risk for child abuse. Child Homicide as a Function of Genetic Relatedness to Offspring • Genetic unrelatedness accounts for most child homicides. • It is found cross culturally as well, as in some tribes you can kill your stepchildren if the woman remarries. Sex Differences in Parenting Adaptations • Primary Caretaker Hypothesis: women will have evolved adaptations that increase the odds that their children will survive. • Females interest in infants peaks in childhood And adolescence to ensure they have enough parenting experience and motivation to successfully raise their first child. • Women are better than men at recognizing facial emotions, this finding is consistent with 2 hypotheses: (1) Attachment Promotion Hypothesis: suggests that women should be better than men at decoding all facial expressions of emotion – responsiveness to infants likely to produce securely attached children. (2) Fitness Threat Hypothesis: predicts a special sensitivity to dangers that might be conveyed by negative emotions. Offspring’s Ability to Convert Parental Care into Reproductive Success • Parents do not only invest into robust and healthy offspring – but sometimes the opposite. • Key theoretical point: it is not whether the child is ill or healthy, but rather the child’s ability to convert a given unit of parental care into fitness. • Parental investment is positively correlated with academic skills, social skills, and subsequent socioeconomic status. - with the father’s investment being more important. • 2 factors that determine which child is invested in more: (1) whether the child is born with abnormality (disabled children are less likely to have reproductive success) (2) the age of the child (younger children are lower in reproductive value) Parental Neglect and Abuse of Children with Congenital Abnormalities • Findings are consistent with the hypothesis that parents invest less in children with abnormalities. - large fraction are institutionalized - 12 % of these were never visited at all - 22% were visited only once a year or less • Children with congenital abnormalities are abused at high rates - ranges from 7.5% - 60% Maternal Care Based on the Health of the Child • Mann, 1992: assessed positive maternal behavior (kissing, holding, soothing, talking to, playing with, and gazing at the infant) from mothers towards their disabled twin vs non- disabled twin - at 8 months old all the mothers directed more positive behavior towards the healthy twin. - therefore supports the healthy baby hypothesis for reproductive success. • Healthy Baby Hypothesis: that the health status of the child would affect the degree of positive maternal behavior. • Recent study suggests that it is dependent upon the income of the mother: - more resources = higher investment in disabled child. - less resources = lower investment in disabled child. Age of Child • Infants are at a much higher risk of being killed by their genetic parents than any other age group of children. • More likely to be killed by genetic parent when young, and unrelated individual when older. • The increasing reproductive value of children as they age accounts for the fact that genetic parents kill older children less often. • 2 negative indicators of the child’s ability to promote the parents reproductive success are: (1) Birth defects (2) Youth • Strong evidence that parents invest more care into
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