Test 3 Flashcards
Cohen’s d
standardized mean difference measuring effect
d = .2
small difference
d = .8
large difference
Age of sex difference in aggression
age 2-4 years
decreases for both sexes as they grow up
Males aggression
higher total aggression
higher physical aggression
Dinsdale, Reddon, and Hurd
males had greater levels of total aggression
anger does not have significant sex difference in aggression type
does not contradict aaron sell
Aaron Sell
Males aggression is linked to physical dominance
Female aggression is linked to attractiveness
Odds ratio
probability of an outcome of an event when there are 2 possible outcomes
odds ratio = 1
equal odds for men and women
odds ratio of <1
of men fighting/# of women fighting
higher odds for women
if effect of males/effect of females
odds ratio of >1
higher odds for men
if effect of males/effect of females
Martin Daly and Margo Wilson
evolutionary psychologists who investigated aggression in their book Homicide
Advantages of studying lethal aggression from evolutionary perspective
show severe and genuine conflict
creates minimal biases in detection and reporting
heavily studied because of the social cost
massive amounts of data in time, place, and history to see patterns of adaptive structuring
Daly and Wilson’s key prediction on homicide
genetic relatedness matters
Methodological challenge when testing homicide in genetically related individuals
how to address the fact that there are differences in availability/mutual access across relationship types
Daly and Wilson approaches to solve methodological challenge
calculating homicide risk by relationship using cohabitants only, and testing collaborative homicide (co-offenders)
Homicide among cohabitants
risk highest for spouses and non-relatives
Genetic relatives more likely to be co-offenders or victim-offenders?
co-offenders
consistent with inclusive fitness theory
Cohabitants and collaborative killing bias
step siblings/step parents are lumped into the “offspring” “parents” and “relatives” categories, removing step-siblings/step parents would increase the amount of killings by non-relatives.
Motivation driving homicide
trivial altercations and insults
male honor, status, and reputation are really what is at stake
Homicide trends
- people kill people of about the same age
- mass of killings occur among adults aged 15-20
- mass of homicides reflecting adults age 20-40 killing children age 0-6, with very young (<1) children most at risk
- small crest indicating young adults that prey upon elderly (eldercide)
Frequent age-related homicide dominated by family members
age of victim was young and age of family member ranged from 10-50, suggest killing of their children
AND age of victim was high, age 80-100, and age of offender was younger, 40-80, suggesting killing of older parents
Uxoricide
killing of the wife by a husband
fillicide
killing of a son/daughter over the age of 1
Theory of male sexual proprietariness
male psychology influenced by the threat of cuckoldry and problem of paternity uncertainty which produced selective pressures to control female reproduction to neutralize threats
Relationship between residency and uxoricide
men kill wives they are separated from at double the rate of wives they co-reside with which can be explained by male mate control due to extreme jealousy/coercion
Relationship between female reproductive value and uxoricide
uxoricide is highest for young wives when reproductive value is highest because men want to control their reproduction
Potential confound of female uxoricide risk and age
young women are more likely to be murdered by husbands because husbands are also young, and young men do most of the killing
evidence against confound of female uxoricide risk
risk of uxoricide is elevated with older husbands
presence of step children increase uxoricide risk
Function of male infanticide
induce earlier resumption of female estrus, force women to be ready to bear children again quicker
select for female counter-strategy of multi-male mating to confuse paternity
Polygyny vs monogamy has more infanticide?
polygyny has higher male infanticide
Increased sex ratio (more females than males) has higher infanticide?
more females has higher male infanticide
increased reproductive skew (dominant male sires a larger percentage of offspring than other males) has higher infanticide?
increased reproductive skew has higher male infanticide
especially if keep power for short time periods
larger testicles has more infanticide?
large testicles has lower male infanticide
paternity confusion
when females mate with multiple males so they are unable to be certain whose child it is
prevents male infanticide because they do not want to risk killing their own offspring
partible paternity
belief that more than one man can contribute to the conception of a fetus
more frequently found in traditional societies of lowland South America
hypothesized function for human filicide/infanticide
paternity uncertainty, inclusive fitness/genetic relatedness, managing tradeoffs between current and future reproduction, offspring sex, threat to father
paternity uncertainty/genetic relatedness
18% attributed to fact that the child was not the parent’s own
limited resources
50% were attributed to unfavorable circumstances (twins, too many children, no male support, being unwed)
STRONGEST SUPPORTED FACTOR
infant viability
19% were attributed to infants being deformed or very ill
maternal age
reproductive value of the women
offspring sex
4% were attributed to the female sex of the infant, but no instances of male sex being cause of infanticide
Trivers-Willard hypothesis
when conditions are favorable, females of a species are expected to give birth to songs, but when conditions are unfavorable, females are expected to give birth to daughters
high quality male can have more offspring than high quality female (evidence is lacking)
greatest risk factor for children for filicide
being a stepchild, having a stepparent
Confounding factors of high rate of stepchildren filicide
many genetic fathers do not live with their children
stepfathers of young children tend to be younger than the father (younger men are more violent)
adjusted, stepfathers look much less lethal
Thomas Hobbes theory on human nature
believed people are naturally violent and strong institutions are needed to curb violence
Jean-jacques Rousseau
believed that people are naturally peaceful and benevolent, institutions are the problems creating inequality and promoting violence
lethal aggression operationalized
increases from mammals to primate to gorillas, chimpanzees, and homo sapiens
estimated rate of lethal aggression in ancestor of all mammals
.3%
estimated rate of lethal aggression in ancestor of all humans
2%
factors associated with evolution of greater lethal aggression in mammals
lethal aggression is higher in territorial species compared to non-territorial species
higher for social species compared to solitary species
Violence in historical age compared to modern age
violence has decreased in the modern age which support Hobbes’s idea that strong institutions are needed to stop violence
sociobiologist that suggested violence in Europe has steadily declined
Norbert Elias author of The Civilizing Process
who introduced parent-offspring conflict theory to biology
robert trivers
key conclusions from parent-offspring conflict theory
extends implications of gene-centric thinking, and Hamiltonian inclusive fitness
children will tend to want more than is optimal for parents to provide
Developmental transitions expected to be intense period of conflict
transitional periods such as weaning, indicated a shift in mother’s investment from current to future offspring
Biologist that extended parent-offspring conflict to maternal-fetal relationship
david haig
genetic conflicts on maternal-fetal relationship
genes that are in the mother but are not in the fetus
genes that are in the fetus that come from the mother
genes that are in the fetus that come from the father
set of genes that weight the welfare of mother’s future offspring most strongly
genes that are in the mother but not in the fetus
set of genes that weight the welfare of mother’s future offspring least strongly
genes that are in the fetus that come from the father
pregnancy phenomena that are conflicts between mother and fetus
spontaneously abort unpromising fetuses before implantation, fetus send deceptively strong signals of viability
fetus release chemicals to manipulate maternal arteries, increase blood flow and resources to fetus but raise maternal blood pressure
optimal blood glucose levels can induce maternal diabetes, offspring of these mothers then to be larger than those of other mothers
cooperation
behavior that provides a benefit to another individual and has evolved at least partially because of this benefit, mechanisms that evolved by natural selection to deliver benefits to others
benefit delivery examples that are not cooperation
salmon leaps into bears mouth, beetle eats elephant poop, insects clump together
why is cooperation an evolutionary problem?
declining average fitness after mutation
2 approaches to solving problems of cooperation
search for indirect fitness benefits
search for direct fitness benefits
by-product mutualism
helping others as a side effect of helping oneself
examples of by-product mutualism
bugs gathering in a circle and territorial chorusing
reward
both cooperate
temptation
one defects
sucker’s payoff
partner defects
punishment
both defect
one shot vs iterated prisoner’s dilemma
one shot is when game is played once, iterated is when it is repeated which allows for strategy based on past moves, allowing for reputation effects and retribution
tit-for-tat strategy
co-operate on the first move, and never be the first to defect
if partner defects, retaliate
if partner returns to cooperation, forgive
direct reciprocity
mechanism where people help those who have helped them in the past
will motivate the recipient to return the same benefit in the future
who introduced direct reciprocity
robert trivers
w>c/b
benefit of value b to recipient today at cost c
w = likelihood of future interaction
hamilton’s rule
rxb>c
relatedness x benefit > cost
3 conditions present in animal species characterized by reciprocal altruism
animal performing altruistic act must have reasonable chance of meeting recipient again to receive reciprocation
reciprocal altruists must be able to recognize each other and detect cheats
ratio cost to donor/benefit to receivers’ must be low
3 conditions for reciprocal altruism in blood sharing vampire bats
stable groups, recognition, cost/benefit ratio low (small donation is highly valuable to recipient)
Alternate explanation of blood sharing
could be harassmen, hungry bats beg to prevent well-feed bats from sleeping
blod sharing may normally involve kin, so sharing might be kin altruism
Best predictor of amount of blood vampire bat shared with other individual
best predictor of amount A shared with B was amount B shared with A (more important than relatedness)
bats competed among themselves to share
key takeaway from investigation of cooperation in prisoner’s dilemma game
more cooperation in the beginning when it was suspected to interact in the future
public goods game
investigate the incentives of individuals who free-ride off individuals who are contributing to the common pool
Key takeaway from paper on public goods game
Effectiveness of punishment varies with its cost
When punishment is cheap, it will be used readily until learning has taken place, then it becomes rare.
When punishment is expensive, it will be used less readily, and learning will be slower, so defection will be more persistent.
indirect reciprocity
cooperator provides a benefit to recipient, recipient does not repay
cooperator acquires good reputation
who introduced indirect reciprocity as mechanism for sustaining cooperation
richard alexander
q>c/b
probability of knowing someone’s history of helpfulness (q) must exceed c/b
study of generosity
men were more likely to be more generous when there was a women observing, women showed no difference based on observer
Yoeli study on observing
people more likely to participate when they could be observed, effects were largest in conditions where reputational concerns were strongest
apartments stronger than houses, owners stronger than renters
Hrushchka’s study of friendship
4 strongest characteristics of friendship: mutual aid, gift giving, positive affect, and need
Function of friendship
generated by cognitive system that function to assemble support group for potential conflicts = alliance politics
predictions on alliance politics
factors predicting how highly person A ranks person B as friend will be how highly person A thinks peron B ranks them
people will be motivated to conceal their friend rankings
Results of function of friendship study
people have preference toward friends, people would mask preferences if points were made publicly available
strongest predictor of friend rank
perceived rank
tragedy of the commons
effect of free riders not contributing but are benefiting from the common good, will deplete the common good and lead people not to contribute
cinderella syndrome
fear of independence will an unconscious desire to be taken care of by others
age crime rate
crime in young men rapidly increases during adolescence and peaks at age 19
crime rates considerably higher for men than women because males drive for status and resources, which signals high reproductive value
mutulaism or reciprocity
recipient gains, initiator gains
selfishness/parasitism
recipient loses, initiator gains
altruism
recipient gains, initiator loses
spite
recipient loses, initiator loses
