Human Behavior Nature, Nurture and Human Diversity
Our behavior is often characterized as “human nature.” • What do we mean by human nature? • How might a psychologist go about identifying the traits of human nature?
In a culture that emphasizes our differences, we sometimes forget just how similar we are…
Brainstorm and list all the universal behaviors (behaviors shared among all cultures) that you can think of… communicate both verbally and nonverbally Enforce rules of etiquette Avoid incest Fear snakes / heights Exchange gifts Modesty in sexual behavior and bodily functions Labor divided by age and sex Men- more aggressive than women Women provide more child care Tools for work Belief systems- death, disease Plan for the future Taboos- crimes and legal punishments Marriage Laugh / smile / mimic / joke / flirt / sympathize / tease / dance / Music /Myths / folklore / poetry Games War
In a world of such diverse cultures, why do so many universal behaviors exist? • Genetic similarities / shared DNA
Just how similar are we? (True or False) • Fraternal twins are no more genetically similar than normal siblings. • If after a worldwide catastrophe only Icelanders or Kenyans survived, the human species would suffer a huge reduction in its genetic diversity. • We share 99.9% of our DNA with our neighbor! (Near clones!) • “We are the leaves of one tree.”
Nature, Nurture and Human Diversity Essential Question: What ultimately shapes our behavior? Topics of Study: Genetics and Evolutionary Psychology Parents, Peers and Culture Gender
Pattern Recognition • Nature v. Nurture • Sugar and spice and everything nice, that’s what little girls are made of…” • “Handsome is as handsome does.” • “Like father like son.” • “You can’t teach an old dog new tricks.” • “Boys will be boys.” • “You are what you eat.” • “Blood will tell.” • “All men are created equal.”
Genetics and BehaviorGetting started….. We know that both nature and nurture weave together to shape our behavior. Its easy to prove that nurture influences behavior, but how could we devise a way to prove that genetics influences our behavior?
Read carefully pages 95-102 1. Identify the following and explain how they collectively influence behavior. chromosomes, DNA, genes, gene complexes Explain specifically how studies contrasting fraternal and identical twins have helped prove that genetics influence individual behavior. The case studies of Jim Lewis / Springer and Oscar Sohr / Jack Yufe (identical and separated at birth) provide evidence that genetics influence’s behavior. Explain specifically the strengths and weaknesses of these studies.
Behavior Genetics • Study individual behavioral differences. (weigh effects of nature, nurture) • Chromosomes: 23 / egg, 23 / sperm (threadlike structures) • Composed of DNA (deoxyribonucleic acid) • Genes: 30,000 each / self-replicating units, synthesize proteins, (the building blocks of physical development • Gene complexes: many genes acting in concert • Genes: Influence physical make-up, intelligence, aggressiveness, happiness etc.
Fraternal: (dizygotic) Separate fertilized eggs (no more genetic similarity than normal siblings) Identical: (Monozygotic) Single fertilized egg split in two = clones Fraternal, Identical Twins:What’s the difference?
Fraternal vs. Identical • Fraternal / Identical twin study findings- provide specifics for the following: • Alzheimer’s • Identical =60% / Fraternal=30% • Extraversion / neuroticism • Identical more similar than fraternal • Divorce rates • Identical x5.5 vs. fraternal x1.6 • Schizophrenia • 50, 10, 3, 1 (identical, fraternal, sibling, stranger) • What are the limitations of these studies? • Genetics or environment? How do we differentiate?
Twin StudiesJim Lewis / Springer • What does the study suggest?
Jim an Jim • 37 days after birth • Romantic- love notes to wife • Son James, dog Toy, wife Linda • Woodworking (same bench in front yard) • Chevy, stock car racing, Miller Lite • Vasectomy, high blood pressure, chain smoker • migraines
Levy and Newman • Bouchard’s Minnesota Twin Study • Reunited by shared acquaintance • Upon meeting for first time: • Same mustache, sideburns, glasses • Levey: college degree in forestry- Newman planned to but worked for city trimming trees • Levey worked installing sprinker systems, Newman installed fire alarms • Both were bachelors, same taste in women • Both only drank Budweiser (pinky wrapped underneath can, crushed can afterwards) • Hunting, fishing, beach, John Wayne movies, pro-wrestling, Chinese food in wee hours • Volunteer firefighters • Both raised Jewish, neither particularly religious • When met- same remarks, at same time, same gestures- “spooky” • He is he and I am I, and we are one…
Genetics and Behavior Why has genetics not been given more consideration as a determiner of personality and behavior? • 2nd ½ of 20th century: behaviorism’s dominance • “Experience as primary architect of human behavior” • “Invisible” genetics- can’t see, touch or remember the influence • Determinism- “compromises free will” • Nurture gives parents measure of confidence- “can control outcome” • Bad, ineffective behavior can be “unlearned” • “Why bother?” Genetic argument reduces free will, cornered by determinism • “That boy was born to act that way!” • Reality: Both play critical role in who you are!
Adoption, Genetics and Behavior • Environmental relatives / biological Relatives • Finding: subject’s personality reflected biological relatives, even when adopted at birth • Conclusion: people who grow up together don’t resemble each other in personality • Why are two people raised together so different??? • Confirmation of genes impact on personality
Environmental Influence • So what traits does nurture influence? • Values • Manners • Faith / religion • Politics • Social views
Temperament • Our emotional excitability • Temperament traits tend to remain consistent through life • Studies confirm • Genetic temperament helps form enduring personality • Think of two examples of those you know.
Heritability • Extent to which difference between individuals can be attributed to genes • As environments become more similar, heredity as a source of difference becomes more important (and vice versa) • Heritable differences don’t often translate to group differences
Nature and Nurture • Genes are self-regulating (respond and adapt to environment) • Individual differences almost always the result of both nature and nurture • “Gene and scene dance together” • Or, “nurture works on what nature endows”
Identify specific genes influence on behavior Weight, extraversion, sexual orientation… LD, depression, schizophrenia, alcoholism… Designer babies?!?! Molecular Genetics
Questions to Consider • 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?
Premise (Darwins’ ) natural selection shapes our behavior, thinking (over time) Certain traits, behaviors that enhance survival are passed on over generations Evolutionary Psychology
30 males, 100 females Tamest 5% M, 20% F 30 generations Complete domestication Now sold as house pets Implications? When certain traits are selected that give a reproductive advantage, those traits will prevail Belyaev’s Experiment
Evolutionary Psychology • For the most part, evolutionary psychology helps to explain our similarities. (Universal behaviors) • But it also helps explain some key differences…….
Evolution and Human Sexuality True or False: Males are more likely than females to initiate sexual activity.
Gender and Sexual Attitudes / Behavior Studies: • 1978, FSU- research assistants / proposals for casual sex with strangers • 75% of men- yes 0% of women- yes • Questionnaire: casual sex with different partners • 48% of men- yes 12 % of women- yes • Question: Why is there a difference between genders concerning attitudes and behaviors about sex?
Women- relational Incubates, nurses one infant Wants protection, assistance to ensure child’s survival Chooses wisely Men- recreational Perpetuate his genes (spread his genes through other females) Chooses widely Gender Differences and SexualityNatural Selection
Men (attracted to…) Youthful, healthy, fertile Waists 1/3 size of hips Many children- genes to future… Women (attracted to..) Mature, dominant, bold, affluent Support and protect Long- term mating, investment in joint-offspring Gender and AttractionStudy spanned 37 cultures
Gender Differences and Sexuality • Significance? • “Nature selects behaviors that increase the likelihood of sending one’s genes into the future.”
In Conclusion… • 4 important gender differences in human sexuality (Comprehensive Study: Letitia Anne Peplau) 1. Men show greater sexual desire than women 2. Women tend to emphasize committed relationships as a context for sexuality (more so than men) 3. Aggression is more closely linked to sexuality for men than women (powerful, domineering, experienced, individualistic) 4. Women’s sexuality shows greater plasticity (attitudes, behaviors about sex more easily shaped by cultural, social factors) • Example: college (liberalizes women’s attitude towards sex more than men’s) • Chance of men identifying as gay or bisexual: x2 • Chance of women identifying as lesbian or bisexual: x900!
Evolutionary Psychology • From an evolutionary psychology perspective, how might we explain marriage?
Nature, Nurture and Gender • Gender Development • Male, Female- What’s the difference? • 23rd pair of chromosomes determine sex • Female=X, Male = X or Y
Men X4 to commit suicide, alcoholism Autism, color blindness, hyperactivity, antisocial personality disorder Women 70% more fat 40% less muscle 5 inches shorter Puberty 2 years earlier Live 5 years longer X2 for depression, anxiety X10 for eating disorders Glad to be your gender?
Gender and Aggression • Males tend to be more physically aggressive • Male-female arrest rate for murder • U.S. 9-1 • Canada 7-1
Gender and Social Power • Universal pattern: Men are more socially dominant • Men: as leaders- more direct, autocratic, express opinions • Women: as leaders- more open, democratic, offer support
Males Individualists Boys: larger play groups (activity focus) Male Answer Syndrome Freedom, self-reliance Females Interdependent (relationships) Girls: smaller groups (often one friend) less competitive, imitate social relationships 85% of greeting cards! More religiously oriented Gender and Social Behavior
Boys, girls and toys…Nature or Nurture? • Why do genders choose what they do…?
Nature and Gender • Prenatal Months • 7th week: develop male, female anatomical distinctions • 4th, 5th month: Ovarian hormones, testosterone influence different brain development • Studies • Hines and Alexander: Texas A&M- Velvet monkeys • 1 day old infants: video: friendly face or mechanical mobile • 1 yr. old infants: films: faces or cars • Evidence suggests cognitive differences upon birth
Nurture and Gender • Gender identity • Social learning theory • Gender Schema theory: Learning theory + cognition • Schema, or concepts are formed by genders in developing stages- 1yr olds: voice gender differences • lens through which they see the world confirms roles
Gender Differences and the Brain • New evidence: structural, chemical and functional differences between genders and brains • Females: thicker frontal lobe (verbal fluency) • Males: thicker parietal Cortex (space perception) • Potential need for sex-specific treatments for addictions, depression, schizophrenia etc.
Genes rule…?? • 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.)