CHAPTER 2 NATURE WITH NURTURE

Chapter 2 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 Dispute over the relative importance of hereditary and environmental factors in influencing human development

Nature vs. Nurture Nature Heredity factors such as our genes and chromosomes that we receive from our parents. Referred to as the environmental factors—how the child is brought up, SES, etc.

DEVELOPMENT IS DRIVEN BY NATURE Preformationism Rousseau’s innocent babes Genetic determinism and eugenics Preformationism—All characteristics of an adult were prefigured in miniature within either the sperm or the ovum. Goes along with Western notions that children are by nature bad—born into original sin. Parents had to keep an eye on children and punish them, evenly severely, for behavior deemed sinful. Rousseau—children are innocent at birth and development unfolds; nature is more important than environment, although he acknowledged environment played a role. Parents needed to nurture children and protect them from harmful interference so this development could unfold. Genetic determinism and eugenics—human qualities are genetically determined and cannot be changed by nurture or education; environment does not matter; led to a really disturbing philosophy called eugenics—the use of controlled breeding to encourage childbearing among people with characteristics deemed “desirable” and discourage or eliminate it among those with “undesirable” traits—often targeting ethnic minority groups.

DEVELOPMENT IS DRIVEN BY NURTURE The Blank Slate Locke’s view of the mind “tabula rasa” Watson’s Behaviorism: strict “fundamentalist” version of environmentalism John Locke’s view in the 17th century that the infant comes into the world with a mind that is a blank slate—nothing about development predetermined, not evil (Puritans) or good (Rousseau)—hence the term tabula rasa which means blank slate. Everything is a product of the environment and experience. It is the parents’ responsibility to teach children. These ideas about nurture dominated the 19th century and into the 20th century. Watson’s theory of behaviorism in the early 20th century saw development as a result of experience in the environment primarily, like Locke.

DEVELOPMENT: PART NATURE, PART NURTURE Heritability Degree to which different traits are influenced by genetic factors Twin studies Adoption studies Family relatedness studies

FIGURE2.2: 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 A gradual process of increasing complexity due to interaction between heredity and the environment: http://www.5min.com/Video/Laurence-Steinberg-on-the-Nature-vs-Nurture-Debate-304230832 Epigenesis: http://learn.genetics.utah.edu/content/epigenetics/twins/

The Genetic Code DNA—the chemical that is the basis for heredity Chromosomes are strands of DNA that carry genes, which are smaller segments of DNA The chromosomes are twisted into a structure that looks like a long spiraling ladder called a double helix The steps of that ladder are made of pairs of chemical units called bases There are 4 bases that are the “letters” of the genetic code: A—Adenine T—Thymine C—Cytosine G—Guanine

The Genetic Code Genes are the units of heredity Each gene is located in a specific position on its chromosome and has thousands of bases The sequence of the bases tells the cell how to make proteins that enable the cells to carry out their particular functions

Genotypes and Phenotypes Phenotype—the observable (expressed) traits and characteristics of a person Genotype—your underlying genetic makeup which contains both the expressed and the unexpressed traits and characteristics

Sexual Reproduction Mitosis Meiosis Mitosis—the process through which cells (other than reproductive cells) divide Each resulting cell gets a full copy of all 46 chromosomes Every cell in your body except the sex cells (sperm and ova) has 23 pairs of chromosomes—46 in all http://www.youtube.com/watch?v=Ba9LXKH2ztU&feature=related Meiosis—the process through which gametes are produced Gametes are reproductive cells—the sperm in males and the ova (eggs) in females Meiosis produces cells with only half a set of chromosomes Through meiosis each sex cell ends up with only 23 chromosomes instead of 46 as in mitosis

Sexual Reproduction Fertilization –2 reproductive cells merge—mother’s and father’s chromosomes link Each person has 2 sets of chromosomes and so has 2 copies of every gene—called alleles http://www.youtube.com/watch?v=2cwXD6Qc-NU&feature=related

What determines sex? XX XY XX XY Girl Boy

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 Additive heredity—a trait is the result of a mix of mother’s and father’s traits—not just one gene is responsible. Sometimes called polygenic inheritance. Explain dominant/recessive inheritance with tongue curling example. Tongue curling is a dominant trait. Regulator genes--

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 microsystems are connected Exosystem –contexts outside the individual’s immediate, everyday experience Macrosystem –larger forces that define a society at a particular point in time