Psych 1101 Chapter 4 Nature Nurture and Human Diversity Genes and Behavior human brain has 100 billion neurons Behavior Genetics the study of our differences seeks to determine the relative importance of heredity and environment on behavior environment includes every nongenetic influence e g prenatal nutrition family environment cellular structure 46 chromosomes 23 donated by each parent each chromosome is composed of DNA deoxyribonucleic acid genes are DNA segments that when active or expressed provide the code for the production of protein molecules genome provides the complete instructions for making an organism consisting of all the genetic material in the organism s chromosomes variations at particular gene sites in the DNA define each person s uniqueness human traits are influenced by many genes interacting with the environment Twin and Adoption Studies comparisons of identical twins genetic clones and fraternal twins who develop from separate eggs help behavior geneticists tease apart the effects of heredity and environment adoption studies enable comparisons with both genetic and environmental relatives adopted parents caregivers separated fraternal twins DO NOT exhibit similarities comparable to those of separated identical twins adoptee s adopted children traits i e fixed traits BEAR MORE SIMILARITIES TO THEIR BIOLOGICAL PARENTS than to their caregiving adoptive parents nonetheless caregivers do influence attitudes values etc Temperament and Heritability temperament refers to an infant s inherent characteristic emotional excitability and intensity some babies easy are more relaxed and cheerful while others difficult are more tense and irritable these differences in temperament tend to endure for example the most emotionally intense preschoolers tend to be relatively intense young adults heritability describes the extent to which variation among members of a group can be attributed to genes heritability the percentage in variation that can be explained by genes Molecular Genes molecular genes is the study the molecular structure and function of genes identify specific genes influencing behavior through prenatal screening we can identify genes that put people at risk for genetically influenced disorders epigenetics examines the molecular mechanisms by which environments trigger genetic expression our genes affect how our environment reacts to AND influences us thus genes are self regulating in that they can react differently in different environments we are all the products of interactions between our 1 genetic predispositions and 2 our surrounding environments example a baby who is genetically predisposed to be social and easygoing may attract more affectionate and stimulating care thereby developing into a warmer outgoing person Evolutionary Psychology evolutionary psychologists focus on what makes us so much alike as humans study how natural selection has shaped our universal behavioral tendencies natural selection refers to the principle that those inherited traits that lead to increased reproduction and survival will most likely be passed on to succeeding generations How Does Experience Influence Development early experiences can modify the brain in the womb embryos receive different nutrition and varying levels of exposure to toxic agents normal stimulation during the early years if critical for optimal brain development experience preserves our activated connections and unused connections degenerate a process called PRUNING throughout life our actions strengthen some neural pathways while others weaken from disuse Development Parent and Peer Influences parental influences clearest at the extremes for example in the abused who become abusive and in the loved but firmly disciplined children who become self confident and socially competent parents are more influential when it comes to education discipline responsibility orderliness charitableness and ways of interacting with authority figures peers are more important for learning cooperation discovering interests and learning styles of interaction among people of the same age Development Cultural Influences culture refers to behaviors ideas attitudes values and traditions shared by a group of people and transmitted from one generation to the next all cultural groups evolve their own norms rules that govern their members behaviors rules for accepted and expected behavior Cultural Differences Individualist Cultures personal goals identity defined by personal attributes personal control individual achievement costs loneliness higher divorce rates higher homicide rates more stress related disease Collectivist Cultures value group goals and solidarity relationships tend to be close and enduring social harmony is important duty to family before personal preferences choices identity derived from belonging goal is to maintain social connections perform one s role Gender Development biological sex is determined by the twenty third pair of chromosome i e sex chromosome the member of the pair inherited from the mother is an X chromosome The X female or Y male chromosome that comes from the father determines the child s sex Based on epidemiological how often something occurs studies men and women similar in intelligence vocabulary and happiness men and women differ in body fat muscle height life expectancy males tend to be more aggressive women more vulnerable to depression anxiety and eating disorders men more likely to commit suicide suffer alcohol dependence diagnosed with autism color blindness attention deficit hyperactivity disorder as children and antisocial personalities as adults Gender Development in surveys men admit to more aggression than women and experiments confirm that men tend to behave more aggressively such as by delivering what they believe are painful electric shocks the same difference is reflected in violent crime rates The gender gap in physical aggression appears in many cultures and across various ages Evidence in means of suicide compared with men women are more concerned with making social connections This gender difference surfaces early in children s play As teens girls spend more time with friends and less time alone Gender Roles and Gender Typing gender is also socially constructed as culture shapes our gender roles a role is a cluster or group of prescribed actions for example gender roles expectations about the way men and women behave vary across cultures times and across generations gender