Reversal: What if males invest more than females? (parental investment theory)

· Males are choosier · Females are larger, more competitive & aggressive

Strategic Pluralism Theory

· Variation in sexual strategies within the sex · Just as much variation within sex as there is between the sexes · Purpose is to look at the variation within sex rather than between the sexes

Life History Theory

· Childhood experiences shape people's mating strategy

Predictable/safe childhood (life history theory) =

· slow reproductive strategy (fewer children and investing large amounts of time and resources to those few)

Unpredictable/dangerous childhood (life history theory) =

· fast reproductive strategy (reach sexual maturity early, start having sex early, have as many children as fast as you can, impulsive)

Life History Theory has implications for:

· Age of menarche · Age of first child · Saving vs. spending

What is the #1 most important trait you look for in a short-term (casual) sexual partner?

Both women and men prioritize physical attractiveness

What can attractive features reflect signs of?

"good genes"

What can symmetry reflect?

A strong immune system

What can attractiveness reflect in women?

fertility and reproductive potential

Facial masculinity

exposure to testosterone masculinizes the face

What can attractiveness partially reflect in men?

testosterone

What does testosterone suppresses?

The immune system

handicap principle

If a man has high T AND is healthy, he probably has very strong immune system (good genes)

What is the best definition of physical attractiveness?

A combination of cues that signals a person's reproductive quality

Maner's Study

· Automatic attentional adhesion to attractive opposite sex faces · Results found greater automatic attention to attractive opposite sex faces when they were in a sexual mood · Those in the sexual desire category that were in committed relationships showed less attention to attractive opposite sex targets · Underlines the importance of long term relationships

Women's menstrual cycle and short term mating

· Women's desire for short-term mating changes across the menstrual cycle · Women's orientation toward short-term mating increases during ovulation • Linked with an increase in estrogen

During ovulation women ...

· women prioritize signs of masculinity · prefer the scent of symmetrical men · Women dress more provocatively around ovulation · Women become more flirtatious, and their partners become more vigilant and jealous · Women more willing to cheat on their partner during ovulation (rather they actually cheat depends on the attractiveness of their partner and available partners)

What happens when women who are on the birth control pill get married, and then go off?

· Women with more attractive partners become more satisfied with their relationships · Women with less attractive partners become less satisfied with their relationships · Birth control suppress hormones and sexual desire

Human pair bonding

· In 95% of mammal species, father provides no parental investment and there is no long-term pair bonding · Humans are one of the rare exceptions: Fathers often invest tremendously in their offspring and they form pair bonds · Why? Human intelligence · Humans are smart & have big brains · Human offspring born underdeveloped and helpless (to accommodate our big brains) · Children benefit from having both parents around · Evolution of the human pair-bond

Attachment system

· originally designed for parent-offspring bonding (exists in many species) · When pair-bonding evolved in humans, attachment system co-opted for long-term mating · Oxytocin drives this system

2 basic dimensions of attachment:

Anxiety and avoidance

Low avoidance and anxiety =

secure attachment

Which attachment style tends to have the best relationships?

Secure

Anxious

· clingy, demanding, and possessive. Can push partners away

Avoidant

Emotionally distant

Sex differences in mate preferences:

· Men value physical attractiveness somewhat more than women do, and somewhat more than they want social status · Women value social status somewhat more than men do, and somewhat more than they want physical attractiveness

Willingness to commit and invest:

· Women prioritize signs of commitment and willingness and ability to invest resources in children

Sex differences in age preferences:

· Women tend to prefer somewhat older men · Older age related to status · Men tend to prefer somewhat younger women · Youth related to fertility (reproductive potential)

Women's primary long term mating strategy:

· find a man who is willing and able to commit and invest resources in offspring

Men's primary long term mating strategy:

· find a woman with high degree of fertility and future reproductive potential

Men's Mate Preferences:

· Men prefer qualities suggesting a woman would make a good parent · Signs of fertility are prioritized · Men partnered with fertile women would have more offspring than those partnered with less fertile women

assortive mating theory

· Individuals with similar levels of desirability as a mate tend to pair off

Do opposites attract?

· In general, people end up with partners who are similar to them · An interesting exception: major histocompatibility complex (MHC)

major histocompatibility complex (MHC)

· Reflects immune system "type" · People prefer those with dissimilar immune system · Produces offspring with more well-rounded immunity

How do we know a person's MHC complex?

The best evidence we have is scent; apparently we can smell the type of immune system a person has and it makes them more attractive

Sex ratio theory

Majority sex is at a disadvantage because of increased competition and mating effort

· Minority sex is at an advantage because of relaxed competition and greater choosiness

Operational sex ratio

of reproductively aged males to females in a given population/community

Imbalanced sex ratio

· More men > increases in long-term relationships, monogamy, lower divorce rate, higher paternal investment (when there is more competition men go to the preferred mating strategies of women)

· More women > less monogamy, higher divorce rate, less paternal investment

Factors that affect parental investment

· The estimated degree of relatedness to a particular child (not a problem for women, big determinate for men) · The ability of a child to convert investment into fitness

Children with two investing parents

· Lower infant & childhood mortality rates · Higher educational attainment · Better health · More positive emotional well-being · Better social skills · Greater adult socioeconomic status · Go off to have their own successful offspring

Statistically speaking, care from which parent is especially predictive?

Father. Because most mother's will invest anyway, father's vary.

Imprinting

· Offspring rapidly learn that parent (or whoever is close) is caregiver · The role of physical touch

Social nesting

· Women prepare for motherhood · Bring family and friends closer - "tend and befriend" · Distance themselves from others/strangers - social selectivity · Vigilance to threats · Decreased risk-taking · Increased attention to signs of aggression in others (ex. Angry faces)

Adoption

· Adopted children often receive same (or even better) investment as biological children · Why? · Adoptive parents are often financially well off · To adopt requires large commitment · Adopted children often need more support

Paternity Certainty

· Fathers invest more when cues signal relatedness (biggest one is resemblance) · Partner fidelity · Resemblance to child · To increase father investment, people exaggerate claims of resemblance · Studies show that infants actually resemble the mom more

Who is expected to invest in parenting more?

· Older women because they have less future reproductive potential, younger women have many childbearing years ahead of them they have a higher reproductive potential, may benefit more from focusing on mating effort (having more kids rather than investing in current kids.

· Children of younger mothers more likely to:

· Be terminated during pregnancy · Put up for adoption · Be neglected, abused, & die

Compared to women, why might men invest less?

· Higher reproductive value from focusing on mating effort · Attractive & high status men less likely to invest (higher opportunity costs of investing in current children)

Parent child conflict:

· Parents & kids have different interests · Each acts in accord with their own reproductive success · Example: Before birth · Preeclampsia - baby hinders mom's ability to regulate blood flow - increases nutrition to baby but increases mom's blood pressure, damages kidneys

sibling rivlary

· Parents: Provide resources equally to offspring (or focus on each child's reproductive value) · Offspring: Get as many resources as possible for themselves

· Parents encourage kids to get along and support siblings more than they want to

Disagreements between parents and siblings:

· Parents desire equal distribution of resources between child and sib · Child wants distribution somewhat in his/her favor, but not drastically unequal (kin selection) · When siblings are not biological siblings (e.g., half-siblings) · Parent still wants equal distribution of resources between child and sib · Child wants highly unequal distribution in his/her favor

Harsh, unpredictable environments (life history theory):

· Faster maturation · More/earlier reproduction · Lower parental investment · More present-focused and impulsive · Feel distant from family

Benign, predictable environments (life history theory):

· Slower maturation · Later/less reproduction · Higher parental investment · Optimistic about future, risk-averse · Feel closer to family

Costs of sexual reproduction:

· Relatively inefficient at transmitting your genes (asexual vs sexual) (< 100% vs 50% of genes passed to next generation) · 2 organisms required · Costs of finding and attracting a partner

Asexual

identical to parents

Sexual

mixture of both parents

The Red Queen hypothesis (explains how and why sexual reproduction evolved):

· Sexual reproduction mixes up the genes that generate immune system functioning ("genetic recombination") · Increases resistance to pathogens

Why is gamete size/mobility important in thinking about mating psychology?

· Larger & less mobile gametes require a larger energetic investment (9 months incubation, etc) · Female gametes are more reproductively "valuable" · Differences in levels of minimum obligatory parental investment serve as the foundation for sex differences in mating psychology · Differences exist in initial minimum obligatory investment

Error management theory:

· Avoid costly errors, even if it means making less costly errors ("smoke detector principle") (snake and stick example)

Sexual overperception bias:

Men overperceive sexual interest from women

· Avoid missing reproductive opportunities

Factors that increase overperception bias:

· When the woman is attractive · When men are in a sexual mindset · When the man (or woman) has power · Power > sexual overperception bias > sexualized behavior

Commitment underperception bias:

Women underperceive commitment from men

· Underestimate long-term commitment intent in men · Avoid reproducing with a man who isn't committed (loss of resources)

2 key predictors of relationship problems

declines in satisfaction and interest in alternative relationship partners

relationship maintenance

· Two strategies people often use: · Derogation of attractive alternatives · Inattention to attractive alternatives

Infidelity and divorce

· More attention to attractive relationship alternatives at baseline > twice more likely to commit infidelity · Attention to attractive relationship alternatives > infidelity > divorce · No derogation of attractive relationship alternatives > infidelity > divorce

Jealousy

· Jealousy stemming from concerns about infidelity contributes to:

· Relationship discord · Divorce · Intimate partner violence

Sex differences in jealousy:

· Sexual jealousy in men reflects paternal uncertainty (threat of cuckoldry) · Emotional jealousy in women reflects threat of commitment loss

Physical aggression:

· Higher in men than women · Plays a key role in male intrasexual competition in other species

Indirect aggression:

· Higher in women than men · Plays a key role in female intrasexual competition · Gossip · Especially toward women perceived as rivals

Why is kinship important?

· r = Average amount of shared genes · Genetic relatedness (r) matters · We do not consciously compute our relatedness to others

Hamilton's rule

· We will perform behavior when cost outweighed by benefits X relatedness · This explains how care for kin could evolve · Again, not a conscious strategy · C < B X R

Identifying kin:

· Childhood exposure · Growing up together creates sense of kinship · The role of familiarity · The role of scent · Mothers and children recognize each other's smell · Siblings may recognize each other, too, but evidence for that isn't as clear · Facial resemblance · Similarity is reliable cue to relatedness

Kinship estimator =

odor, similarity, childhood exposure, and kin classification systems

Incest aversion

disgust helps avoid kin incest

Why not form romantic relationships with kin?

· Incest with close genetic relatives increases the risk of obtaining deleterious gene alleles & impairs genetic diversity · Problem declines as "r" decreases · First-cousin marriages relatively common in many countries and in past · Second-cousin appears safest cutoff

Kin in modern times

· Lack of proximity to kin can cause feelings of alienation and anxiety · Mismatch between current and ancestral environments