Myers’ EXPLORING PSYCHOLOGY (7th Ed) Chapter 3 The Nature and Nurture Of Behavior James A. McCubbin, PhD Aneeq Ahmad, Ph.D. (modified by Ray Hawkins, Ph.D.) Worth Publishers

Genes: Our Biological Blueprint To what extent are we shaped by our heredity (nature) and by our life history (of our nurture)? Chromosomes threadlike structures made of DNA that contain the genes DNA (deoxyribonucleic acid) complex molecule containing the genetic information that makes up the chromosomes has two strands-forming a “double helix”- held together by bonds between pairs of nucleotides

Genes: Our Biological Blueprint biochemical units of heredity that make up the chromosomes a segment of DNA capable of synthesizing a protein Each human is estimated to have about 30,000 genes. We are 99.9 similar in our DNA Human traits are influenced by gene complexes---many genes acting in concert (e.g., intelligence)

Genes: Their Location and Composition Nucleus Chromosome Gene Cell DNA

Genetics: Mendelian Theory

Evolutionary Psychology Natural Selection the principle that, among the range of inherited trait variations, those that lead to increase reproduction and survival will most likely be passed on to succeeding generations Mutation: a random error in gene replication that leads to genetic damage Of our .10% genetic differences, 6% are differences among races, 8% are differences within a race, and over 85% are individual variations within local groups. Why are we so much alike?

Evolutionary Psychology the study of the evolution of behavior and the mind, using the principles of natural selection Example: breeding “friendly” foxes (Belyaev & Trutt) (Myers’ text, p. 74-75). Gender in psychology, the characteristics, whether biologically or socially influenced, by which people define male and female.

Evolutionary Psychology Men preferred attractive physical features suggesting youth and health Women preferred resources and social status Critique: “post hoc ergo propter hoc” / backward reasoning. Wood & Eagly (2002) found that in cultures with gender equality these gender differences in mate preferences are much smaller (Myers text, p. 78). Film

Behavior Genetics Behavior Genetics study of the relative power and limits of genetic and environmental influences on behavior Environment every nongenetic influence, from prenatal nutrition to the people and things around us (shared and non-shared environmental effects) (Cohen, 1999, Stranger in the Nest)

Behavior Genetics Identical Twins Fraternal Twins Same sex only Same or opposite sex Identical Twins develop from a single fertilized egg that splits in two, creating two genetically identical organisms Fraternal Twins develop from separate eggs genetically no closer than brothers and sisters, but they share the fetal environment

On Twins… Monozygotic twins = start as 1 fertilized egg (zygote), then split into 2 identical embryos Fraternal twins- only as genetically similar as non-twins (dizygotic) MZ adopted into separate homes Often raised without knowledge of twin In different, contrasting environments

Example Study (from Niederhoffer, 2004 lecture) 56 sets of MZA (reared apart) From 8 countries Intensive psychological and physiological tests and measurements Nearly 50 hours of testing Life history, psychiatric interview, checklists of household belongings, family environment scale, intelligence, personality, etc. IF environment = responsible for individual differences, MZT from same environment should be more similar than MZA…

Comparison of correlations for MZA (apart) and MZT (reared together) CHARACTERISTIC R(MZA) R(MZT) Physiological Brain wave activity .80 .81 Blood Pressure .64 .70 Heart Rate .49 .54 Intelligence .78 .76 Personality .50 .49 Interests .40 .49 Religiosity .49 .51 Social Attitudes .34 .28

Behavior Genetics Temperament Interaction a person’s characteristic emotional reactivity and intensity Bokhorst et al. (2004) attachment security and temperament. Suomi video, “Bringing up Monkey” Interaction the effect of one factor (such as the environment) depends on another factor (such as heredity)(e.g., aggressive child may be yelled at by the teacher) Film

Environmental Influence

Environmental Influence Two placental arrangements in identical twins

Environmental Influence Experience affects brain development Impoverished environment Rat brain cell Enriched

Environmental Influence A trained brain (Myers’ text, p. 80) Left (untrained) Right (trained)

Environmental Influence Peer Influences on development may exceed parental influences (Harris, 1998, Myers’, p. 81) Culture the enduring behaviors, ideas, attitudes, and traditions shared by a large group of people and transmitted from one generation to the next Norm an understood rule for accepted and expected behavior---these may differ cross-culturally. Personal Space: the buffer zone we like to maintain around our bodies Culture and Child Rearing Example: Westernized cultures’ emphasis on individualism, in contrast to collectivism Developmental similarities across groups In surface ways we may differ, but as members of one species we are subject to psychological forces which are generally similar

The Nature and Nurture of Gender X Chromosome the sex chromosome found in both men and women females have two; males have one an X chromosome from each parent produces a female child Y Chromosome the sex chromosome found only in men when paired with an X chromosome from the mother, it produces a male child

The Nature and Nurture of Gender Testosterone the most important of the male sex hormones both males and females have it additional testosterone in males stimulates growth of male sex organs in the fetus development of male sex characteristics during puberty The Nurture of Gender: Gender Roles A role is a set of expectations (norms) about a social position defining how those in the position ought to behave

The Nature and Nurture of Gender Gender Role a set of expected behaviors for males and females biology and evolution may predispose gender roles, but cultural factors and individual differences are also influential (e.g., Spence & Helmreich, EPAQ scales). Gender Identity one’s sense of being male or female Gender-Typing the acquisition of a traditional masculine or feminine role

The Nature and Nurture of Gender

The Nature and Nurture of Gender Social Learning Theory theory that we learn social behavior by observing and imitating and by being rewarded or punished Gender Schema Theory theory that children learn from their cultures a concept of what it means to be male and female and that they adjust their behavior accordingly

The Nature and Nurture of Gender Two theories of gender typing