Human Behavior Nature vs Nurture Nature or Nurture

Human Behavior Nature vs. Nurture

Nature or Nurture? n Why do men and women have such different attitudes about sex? n Why do boys and girls play with different toys? n Why do you, the oldest, seem to be organized and responsible, while your youngest brother seems to be carefree and happily irresponsible?

Behavior Genetics (Text Question #1) n Study individual behavioral differences. (weigh effects of nature, nurture) Ø Chromosomes: 23 / egg, 23 / sperm (threadlike structures) ØComposed of DNA (deoxyribonucleic acid) ØGenes: 30, 000 each / self-replicating units, synthesize proteins, (the building blocks of physical development ØGene complexes: many genes acting in concert n Genes: Influence physical make-up, intelligence, aggressiveness, happiness etc.

Behavior Genetics

Nature and Gender n Gender Development ØWhat determines male, female offspring Ø 23 rd pair of chromosomes determine sex ØFemale=X, Male = X or Y

Fraternal, Identical Twins: What’s the difference? n Fraternal: (dizygotic) Ø Separate fertilized eggs (50% shared genes- no more genetic similarity than normal siblings) n Identical: (Monozygotic) Ø Single fertilized egg split in two = clones (100% shared genes)

Fraternal vs. Identical (#2) n Fraternal / Identical twin study findings- provide specifics for the following: Ø Alzheimer’s Ø Identical =60% / Fraternal=30% Ø Extraversion / neuroticism Ø Identical more similar than fraternal Ø Divorce rates Ø Identical x 5. 5 vs. fraternal x 1. 6 Ø Schizophrenia Ø 50, 10, 3, 1 (identical, fraternal, sibling, stranger) n What are the limitations of these studies? Ø Genetics or environment? How do we differentiate?

Gerald Levy and Mark Newman Bouchard Minnesota Twin Study

Levy and Newman n Bouchard’s Minnesota Twin Study Ø Ø Reunited by shared acquaintance Upon meeting for first time: Ø Same mustache, sideburns, glasses Ø Levey: college degree in forestry- Newman planned to but worked for city trimming trees Ø Levey worked installing sprinker systems, Newman installed fire alarms Ø Both were bachelors, same taste in women Ø Both only drank Budweiser (pinky wrapped underneath can, crushed can afterwards) Ø Hunting, fishing, beach, John Wayne movies, pro-wrestling, Chinese food in wee hours Ø Volunteer firefighters Ø Both raised Jewish, neither particularly religious Ø When met- same remarks, at same time, same gestures- “spooky” Ø He is he and I am I, and we are one…

Adoption Studies (#5)

What insight has adoption studies provided regarding the influence of genetics on personality? (#5) n Environmental relatives / biological Relatives n Finding: subject’s personality reflected biological relatives, even when adopted at birth n Conclusion: people who grow up together don’t resemble each other in personality n Why are two people raised together so different? ? ? ØConfirmation of genes impact on personality

Environmental Influence n So what traits does nurture influence? ØValues ØManners ØFaith / religion ØPolitics ØSocial views

Heritability (#6) n Extent to which difference between individuals can be attributed to genes ØAs environments become more similar, heredity as a source of difference becomes more important (and vice versa) ØHeritable differences don’t often translate to group differences

Temperament (#7) n Our emotional excitability ØTemperament traits tend to remain consistent through life ØStudies confirm ØGenetic temperament helps form enduring personality

Nature and Nurture n Genes are self-regulating (respond adapt to environment) n Individual differences almost always the result of both nature and nurture – “Gene and scene dance together” – Or, “nurture works on what nature endows”

Molecular Genetics (#8) n Identify specific genes influence on behavior Ø Weight, extraversion, sexual orientation… Ø LD, depression, schizophrenia, alcoholism… Ø Designer babies? !? !

Evolutionary Psychology Ø Premise Ø (Darwins’ ) natural selection shapes our behavior, thinking (over time) Ø Certain traits, behaviors that enhance survival are passed on over generations

Questions to Consider 1. 2. 3. 4. Why do infants start to fear strangers about the time they become mobile? Why are most parents so passionately devoted to their children? Why do so many more people have phobias about spiders and snakes than guns and electricity? Why are men quicker to perceive friendliness as sexual interest?

Dmitry Belyaev: Domestication of Foxes

Belyaev’s Experiment n n n 30 males, 100 females Tamest 5% M, 20% F 30 generations Complete domestication Now sold as house pets Implications? n When certain traits are selected that give an adaptive advantage, those traits will prevail n

Gender and Sexual Attitudes / Behavior Studies: Ø 1978, FSU- research assistants / proposals for casual sex with strangers v 75% of men- yes 0% of women- yes Questionnaire: casual sex with different partners Ø 48% of men- yes 12 % of women- yes Ø Ø How can we explain this radical difference in sexual attitudes between the genders?

Gender Differences and Sexuality Natural selection would suggest that each gender pursued attitudes and behaviors that perpetuated their survival, and thus became part of our DNA over time. n Women- relational Ø Incubates, nurses one infant Ø Wants protection, assistance to ensure child’s survival Ø Chooses wisely n Men- recreational Ø Perpetuate his genes (spread his genes through other females) Ø Chooses widely

Boys, girls and toys… Nature or Nurture? n Why do genders choose what they do…?

Nurture and Gender Nurture influences our sense of gender by… Gender identity (one’s sense of being male or female) n Gender roles- traditional behaviors, duties of genders n Gender-typing: expectation or assignment of traditional male, female roles n n Social learning theory (Observation, imitation)

Genes rule…? ? n In terms of personality, environmental factors typically account for less than 10% of children’s differences. (Key is how parents and peers influence those traits. )

Nurture and Early Development n Early experience matters! ØFosters neural connections ØExperience preserves activated neural connections ØUnused ones degenerate (pruning) ØExcess “connectors” in youth make kids more capable of mastering certain tasks. ØExample? ØForeign language, (Accent and grammar) visual perception, musical instruments

Rat Studies n Rosenzweig and Krech Ø Isolated, impoverished vs. social, enriched environment Ø Young rats n Findings: Ø Obvious differences in behavioral activity and curiosity Ø Heavier, thicker brain cortex (brain weight increased 7 -10 percent and # of synapses increased 20%!) Impoverished environment Rat brain cell Enriched environment Rat brain cell

Premature Babies n Neonatal units ØMassage therapy stimulates growth ØSpeeds departure from hospital

Nurture’s Sway… Cultural Influences n Individualism Ø Self: Independent Ø Life Task: Discover, express one’s uniqueness Ø What matters: Me, personal achievement, rights, freedoms, self-esteem Ø Coping method: change reality Ø Relationships: Many, often temporary, confrontation acceptable Ø Behavior: Reflects one’s personality, attitude n Collectivism Ø Self: Interdependent Ø Life Task: fit in, perform role, obligations Ø What matters: Us, group goals, family duty, social responsibility Ø Coping method: Accommodate to reality Ø Relationships: Few, close and long term, harmony valued Ø Behavior: social norms and roles

Cultural Influences n Individualism n Collectivism