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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
This is a 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.
Nurture
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
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 non-
nurturant 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.
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