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

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 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.