CHAPTER 2 NATURE WITH NURTURE
IN THIS CHAPTER How have ideas about nature and nurture changed? What are genes? What exactly do they do? What is the environment? How do the genetic code and environmental contexts interact in development?
PERSPECTIVES ON NATURE AND NURTURE Development is driven by nature. Development is driven by nurture. Development is part nature, part nurture. Development results from the interplay of nature and nurture
NATURE VS. NURTURE This is a dispute over the relative importance of hereditary and environmental factors in influencing human development.
Nature Nurture Heredity factors such as our genes and chromosomes that we receive from our parents. Referred to as the environmental factors: such as how the child is brought up; Culture, Social, Economic, etc.
DEVELOPMENT IS DRIVEN BY NATURE Preformation: The theory of inheritance that hypothesizes that all characteristics of an adult are prefigured in miniature within either the sperm or the ovum Rousseau s innocent babes Children are innocent at birth and develop according to nature s plan. Genetic determinism and eugenics Individual cannot be changed by nurture or education. Advocate controlled breeding to encourage childbearing among people with desirable characteristics.
DEVELOPMENT IS DRIVEN BY NURTURE The Blank Slate Locke s view of the mind tabula rasa Watson s Behaviorism Strict fundamentalist version of environmentalism
DEVELOPMENT IS PART NATURE, PART NURTURE Heritability Degree to which different traits are influenced by genetic factors Twin studies Adoption studies Family relatedness studies
FIGURE 2.2: HERITABILITY OF TRAITS IN TWINS
DEVELOPMENT RESULTS FROM THE INTERPLAY OF NATURE AND NURTURE Contemporary view of relationship between nature and nurture Darwin s Influence Theory of evolution Survival of the fittest and natural selection Epigenesis A gradual process of increasing complexity due to interaction between heredity and the environment
FIGURE 2.3: A HUMAN EMBRYONIC STEM CELL
WHAT ARE GENES? Genes direct the cells of an embryo to become a human being.
HUMAN DIVERSITY No two human beings have the exact same genes. Gene is a segment of chromosomes that control particular aspects of production of a specific protein. 23 pairs of chromosomes = genotype a package of biochemical information that is yours alone. Your observable characteristics = phenotype
DETERMINATION OF SEX
SEXUAL REPRODUCTION Mitosis cell reproduction Meiosis production of sperm and ova Fertilization each individual receives two copies of every gene (alleles)
GENE-GENE INTERACTION Sex determination Additive heredity Child s visible traits, phenotype, is mix of mother s and father s traits Dominant/Recessive heredity One version of gene dominant over another Regulator genes Some genes turn other genes on and off Environmental influences
ECOLOGICAL PERSPECTIVE Bronfenbrenner compared context of development to Russian nested dolls. Microsystems setting in which individual interacts with others face-to-face every day Mesosystem ways in which micro-systems are connected Exosystem contexts outside the individual s immediate, everyday experience Macrosystem larger forces that define a society at a particular point in time
VIDEO: RESILIENCE: HOMELESSNESS
URIE BRONFENBRENNER 1917-2005 ECOLOGICAL SYSTEMS THEORY
FIGURE 1.1: ECOLOGICAL MODEL OF DEVELOPMENT
Human development occurs in context -- It is both influenced by it and influences it in a bi-directional way, in a hierarchical way.
According to this model, the child does not enter the world as a blank slate, but is equipped with a rich evolutionary heritage.
The contexts of human development are varied: The culture in which a child is born, the particular period in history, the subculture and community, the child's family, the immediate surroundings.
Humans: seek social stimuli, attend to human speech, form attachment patterns to caregivers, have a facility for learning a language, and have an interest in explaining and mastering the world around them.
Development in context. The model is depicted in concentric rings, or nested structures, each one influencing those inside it.
MICROSYSTEM Activities and relationships and interaction patterns in the child s immediate surroundings.
MESOSYSTEM This system provides the connection between the structure of the child s microsystem. i.e. home, school, neighborhood, day care center.
EXOSYSTEM Social settings that do not contain children but nevertheless affect their experience in immediate settings. For example, parent s workplace, extended family, and friends.
MACROSYSTEM It is not a specific context, but consists in the values, laws, customs, and resources of a particular culture.
CHRONOSYSTEM This system encompasses the dimension of time as it relates to the Child s environment.
ENVIRONMENTAL EFFECTS ON GENE EXPRESSION Factors such as temperature, light, nutrients, and other chemicals affect proteins produced by body. The nurturant rat studies Whether rat pups raised by nurturant or nonnurturant moms affected expression of genes regulating the stress response Those raised with nurturant mothers showed less hormonal response to stress as adults
ENVIRONMENTAL EFFECTS ON HERITABILITY Heritability varies from one group to another. Environment changes the heritability of a trait. Genetic factors matter less when characteristic is already pretty much determined by environment.
GENOTYPE-ENVIRONMENT INTERACTION Inherited traits lead to different characteristics in different contexts. Reaction range inherited traits as an array of possibilities rather than fixed points
FIGURE 2.7: REACTION RANGE
GENOTYPE-ENVIRONMENT CORRELATIONS Passive gene-environment correlations Parents provide both genes and environments for their children. Evocative gene-environment correlations Genotypically different individuals elicit different responses from their environments. Active gene-environment correlations Correlations occur because individuals select contexts that they find stimulating and rewarding.