EnvironmentEnvironmental Influences al Influences on Behavioron Behavior

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Parents and PeersParents and Peers

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We have looked at how genes influence our developmental differences. What

about the environment, how do our early experiences, our family, our community and culture affects these differences?

Parents and Early Experiences

We begin with prenatal environment.

Prenatal EnvironmentPrenatal Environment

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Identical twins who share the same placenta (b) are more alike than those

who don’t (a), suggesting prenatal influences on psychological traits.

Experience and Brain Experience and Brain DevelopmentDevelopment

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Early postnatal experience affects brain development. Rosenzweig et al. (1984)

showed that rats raised in enriched environments developed thicker cortices than those in impoverished environment.

Brain Development and Brain Development and AdulthoodAdulthood

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Brain development does not stop with adulthood. Throughout our life brain tissue continues to grow and change.

A well-learned finger tapping task leads tomore motor cortical neurons (right) than baseline.

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Parental InfluenceParental Influence

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Parental influence is largely genetic. Indeed this support is essential in nurturing children, however, other

socializing factors also play an important role.

Although raised in the same familysome children are more risk takers.

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Peer InfluencePeer Influence

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Children like adults attempt to fit into a group by conforming. Peers are

influential in such areas as learning to cooperate with others, gain popularity,

and develop interactions.

Cultural InfluencesCultural Influences

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Humans have the ability to evolve culture. Culture is composed of

behaviors, ideas, attitudes, values and traditions shared by a group.

Variation Across CultureVariation Across Culture

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Cultures differ. Each culture develops norms – rules for accepted and expected behavior. Men holding hands in Arabia is

normal (closer personal space) not in American culture.

Gender DevelopmentGender Development

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Based on genetic makeup males and females are alike, especially since the

majority of our inherited genes (45 chromosomes are unisex) are similar.

Males and females differ biologically in body fat, muscle, height, onset of

puberty, and life expectancy.

Gender Differences in Gender Differences in AggressionAggression

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Men more than women express and behave in aggressive ways. This

aggression gender gap appears in many cultures, and at various ages.

In males the nature of this aggression is physical.

Biology of SexBiology of Sex

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Biological sex is determined by the twenty-third pair of chromosomes. If XX then a female is produced, or if XY, then a male

child is produced.

Sexual DifferentiationSexual Differentiation

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In the mother’s womb the male fetus is exposed to testosterones (because of Y

chromosome) which leads to the development of male genitalia.

If low levels of testosterones are released in the uterus the result is a female.

Sexual DifferentiationSexual Differentiation

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Sexual differentiation is not only biological but also psychological and social.

However, genes and hormones play a very important role in defining gender,

especially altering the brain influencing gender differences.

Gender RolesGender Roles

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Our culture shapes our gender roles — expectations of how men and women are

supposed to behave.

Gender Identity — means a how a person views himself or herself in terms of

gender.