CHAPTER 4 Nature, Nurture, and Human Diversity

Transcription

1 CHAPTER 4 Nature, Nurture, and Human Diversity

2 CHAPTER 4 OVERVIEW Behavioral Genetics: Predicting Individual Differences Genes: Our Codes for Life Twin and Adoption Studies Temperament, Heredity, and Personality Gene-Environment Interactions Evolutionary Psychology: Understanding Human Nature Natural Selection and Adaptation Evolutionary Success Helps Explain Similarities An Evolutionary Explanation of Human Sexuality Parents and Peers Parent and Early Experiences Peer Influence Cultural Influences Variation Across Cultures Variation Over Time Culture and the Self Culture and Child-Rearing Developmental Similarities Across Groups Gender Development Gender Similarities and Differences The Nature of Gender The Nurture of Gender Reflections on Nature and Nurture

3 INTRODUCTION Do certain universal behaviors occur across people? Countries? Cultures? What causes our striking diversity but also our shared human nature? Environment: every nongenetic influence, from prenatal nutrition to the people and things around us. Behavior genetics is the study of the relative power and limits of genetic and environmental influences on behavior.

4 THE HUMAN BUILDING BLOCKS

5 GENES: OUR CODES FOR LIFE Within the nucleus of a each cell lies the genetic potential for an individual, in the form of 46 chromosomes These chromosomes are composed of DNA, a double-helix strand that contains genes, which code for specific proteins Genome: the complete instructions for making an organism, all of the genetic material in that organism s chromosomes

6 TWIN AND ADOPTION STUDIES Used to tease apart the influences of environment and heredity: Control home environment while varying heredity (sibling studies) Control heredity while varying home environment (adoption studies) Separated Twins Jim Lewis and Jim Springer (page 137) Biological versus Adoptive Relatives Personality is far more similar to biological parents than the caregivers (adoptive parents) Environmental effects are far outweighed by heredity.

7 TEMPERAMENT AND HEREDITY Temperament: a person s characteristic emotional reactivity and intensity. Temperament differences that persist: Emotionally reactive newborns tend to be the most emotionally reactive 9-month-olds (Wilson & matheny, 1986; Worobey & Blajda, 1989) Inhibited and fearful 2-year-olds are still relatively shy at age 8; half will become introverted adolescents (Kagan et al., 1992, 1994). Emotionally intense preschoolers tend to become intense young adults (Larsen & Diener, 1987).

8 EVOLUTIONARY PSYCHOLOGY: UNDERSTANDING HUMAN NATURE Evolutional psychology is the study of the evolution of behavior and the mind, using principles of natural selection Natural selection: those traits that lead to increased reproduction and survival will most likely be passed on to succeeding generations 1. Organisms varied offspring compete for survival 2. Certain biological and behavioral variations increase their reproductive and survival chances in the environment 3. Offspring that survive are more likely to pass their genes to ensuing generations 4. Thus, over time, population characteristics may change Fox Example

9 AN EVOLUTIONARY EXPLANATION OF HUMAN SEXUALITY Having faced the same challenges throughout our history, men and women have adapted in similar ways. Gender differences in Sexuality: Gender versus Sex Behaviors related to reproduction (Schmitt, 2005, 2007). Women: more relational Men: more recreational Nature selects behaviors that increase the likelihood of sending one s genes to the future.

10 EVOLUTIONARY PSYCHOLOGY CONTINUED Drawbacks to this perspective: It is difficult for evolutionary psychology to follow the scientific method: starts with an effect and works backward to propose an explanation. Social consequences: suggestion of genetic determinism, may rationalize unhealthy relationship patterns. Fails to consider the role of the environment.

11 RECAP Behavioral genetics: relative power and limits of environmental and genetic contributors. Twin, adoption and family studies Heredity outweighs environment Temperament example Evolutionary Psychology: study of the evolution of behavior and the mind, using principles of natural selection Natural selection Sexuality example Drawbacks to this perspective

12 PARENTS AND PEERS To what extent are our lives shaped by early stimulation, by parents, and by peers? Evidence from animal research: Rats living in enriched environments have a heavier cortex and more neuronal connections (more dendrites) than their counterparts in impoverished environments (Rosenzweig & Krech)

13 PARENTS AND PEERS Both nature and nurture sculpt synapses: experience triggers pruning. Pruning follows a period during infancy of exuberant brain growth characterized by extensive addition of dendrites and synapses. Unused neural connections die off, leaving the previously used connections more efficient. Simply stated: use it or lose it

14 PARENTS AND PEERS CONTINUED How much credit (or blame) do parents deserve? Parents/caregivers do play a role; specifics vary. What do parents choose for their children? Parents tend to choose the environment by selecting the neighborhood and schools, the peers are part of this environment. Peers are one medium of cultural influence Peers provide an additional avenue for learning they can model helpful or harmful behaviors Deviancy training

15 CULTURAL INFLUENCES What is a culture? Culture: the enduring behaviors, ideas, attitudes, values, and traditions shared by a group of people. Culture is shared with the next generation. Each generation chooses to keep or abandon certain aspects of culture. Variations Across Cultures Norm: an understood rule for accepted and expected behavior. Norms prescribe proper behavior. E.g. personal space, expressiveness, pace of life Some aspects of culture vary widely even within the U.S. E.g. pace of life

16 CULTURE AND THE SELF Cultures vary in the extent to which they give priority to the nurturing and expression of personal identity or group identity. Individualism: giving priority to one s own goals over group goals and defining one s identify in terms of personal attributes Most common in North America, Western Europe, Australia, or New Zealand Collectivism: giving priority to goals of one s group and defining one s identity accordingly Group identifications provide belonging, values, a network of caring individuals, security

17 VALUE CONTRASTS IN INDIVIDUALIST AND COLLECTIVIST CULTURES

18 GENDER DEVELOPMENT Our biological sex in turn helps define our gender, the biological and social characteristics by which people define male or female, (Myers, 2011, p. 126). How do nature and nurture together form our gender? 23 rd pair: Mother contributes X chromosome, Father contributes X or Y chromosome XX = female XY = male Nature of gender: 4-5 th month of prenatal development: Circulating sex hormones Potential for errors Note gender differences in aggression, social power, social connectedness as discussed in the chapter.

19 Biological differences between male and female brains 1. Cells: men have 4% more neurons, 100 grams more of brain tissue 2. Connections: women have more dendritic connections and myelination 3. Corpus callosum: larger in women greater access to both sides of the brain in processing 4. Language: more lateralized (left) in men, language areas larger in women 5. Inferior parietal lobule (IPL): larger in men, left side larger in men while right side is larger in women

20 NURTURE OF GENDER Gender role: a set of expected behaviors for males or females Can be specific to culture or family Cultural attitudes toward gender roles vary over time Gender identity: our sense of being male or female Social learning theory: behavior is learned by observing and imitating others Parental modeling Gender schemas

21 REFLECTIONS ON NATURE AND NURTURE

22 NATURE AND NURTURE The nature versus nurture controversy is one of the most heavily debated topics in the field of Psychology Gene-environment interaction: From conception onward, we are the product of a cascade of interactions between our genetic predispositions and our surrounding environments (Myers, 2010, p. 142).

23 CONCLUSIONS FROM CHAPTER 4 Behavioral Genetics allows the understanding and prediction of individual differences. Evolutionary Psychology, despite the drawbacks, does help us comprehend evolution s impact on the mind. Parents, peers, and culture greatly influence development. The similarities and differences of males and females are strongly influenced by their genes and their environment. Reflections on Nature and Nurture: Please read this section carefully and consider your own opinions on the topic of nature versus nurture.

24 CHAPTER 4 LEARNING OBJECTIVES Behavioral genetics: Describe behavioral genetics, DNA, chromosomes, and genes. What is temperament? How is it influenced by genes and the environment? Evolutionary Psychology What is evolutionary psychology? Describe natural selection. Parents and Peers: Describe the role of early environment in brain development. Cultural Influences Describe culture. What is a cultural norm? Distinguish collectivist and individualist cultures. Gender Development Distinguish gender and sex. Describe similarities and differences in males and females (use evidence from the book). What are the roles of nature and nurture in gender development?