The Nature and Nurture of Behavior

Let’s start with genetics . . .

Gene A stretch of DNA that produces a specific protein,

which in turn forms building blocks of our bodies or drives the processes that allow us to live

DNA (deoxyribonucleic acid): molecule that contains genes

Human instruction manual: genes affect physical features, such as eye color and height, and behavior

Dogs are bred for genetic disposition/behavior One gene in fruit flies can be altered to produce courtship

behavior between two males

Genetics: Tour the Basics Go to:

http://learn.genetics.utah.edu/

Tour: “The Basics and Beyond”

The Human Genome Project

Genome: the complete instructions for making an organism

Project ran from 1990-2003 (completed 2 years ahead of schedule http://www.ornl.gov/sci/techresources/

Human_Genome/project/ What are some of the social and ethical

implications for genetic screening?

Darwin’s Natural Selection Key is genetic fit with environment Mutation

Depending on environment, genetic makeup or organisms evolves throughout generations of offspring, producing changes in the dominant physical features and behavior of a group of organisms

Evolutionary Psychology

Using principles of natural selection, focuses on the evolution of behavior and the mind

Evolutionary psychologists study how natural selection favoured behavioural tendencies in order to explain commonalities in language learning, attention, perception, memory, sexual behaviour, reasoning and more.

Evolutionary Psychology

All organisms including humans are “gene-producing machines” with the basic motivation of perpetuating their own genetic pool.

Our genes predispose us to act in ways that enhance chances of surviving and spreading’ this motive underlies are behaviour

Evolutionary Psychology

Critics: Evolutionary psychologists make to

many hindsight explanations They underestimate the role of

culture

Evolutionary Theory: The Misunderstandings

Genetic Determinism – the idea that only genes control behaviour. In fact, human behaviour cannot occur without: Evolved adaptations Environmental influences

Evolutionary Theory: The Misunderstandings

That adaptive mechanisms are “optimally designed”– evolutionary psychologists recognize that the environment keeps changing, but evolution occurs slowly (humans are better designed for earlier environments)

Evolutionary Psychology Mating behaviors

One of the most studied areas in evolutionary psychology

Why do we find certain characteristics attractive in a potential mate?

Sexuality Task:

Write down 5 or 6 attributes that you look for in a mate

Handout 3-3 Comparison of Characteristics

Evolutionary Psychology – Gender Differences in Attraction

Women prefer economic resources & older partners

Men prefer physical attractiveness & younger partners

These differences may arise from the different social roles the genders have historically held or because of evolutionary factors These differences are more typically seen in

cultures with gender inequalities

The Coolidge Effect

What is it?

What would be the evolutionary explanation for the Coolidge effect?

Behavioral Genetics Researches in this field study the contribution

of heredity to individual differences in personality, mental ability, and other human characteristics

How much of the differences among people are due to their genes and how much are due to the environment? Genes cannot be described in isolation: they can

only be characterized in relation to the environments in which they operate

Nature vs. Nurture

No one argues in terms of nature or nurture today, but rather scientists understand that heredity and environment interact to produce not only our psychological traits but even our most physical traits (i.e. body weight)

Nature-Nurture: Body Weight

Previous belief: emotional disturbance, heaviness caused by over-eating

Now: set-point (the weight you stay at when you are not trying to gain or lose)

In U.S., half of adult population is overweight – obesity genes have not changed that fast.

Twin Studies Identical twins: same egg, same genes,

thus they develop from a single fertilized egg. May have separate placentas. Zygote splits (monozygotic)

Fraternal twins: different eggs, different genes, thus they develop from two fertilized eggs. They have separate placentas. Genetically no more similar than siblings. Two separate zygotes (dizygotic)

Identical Twins

More similar than fraternal twins in: Abilities Personality traits Interests Emotional stability Attitudes towards reading Playing sports Assisted suicide Divorce (5.5 times more likely compared to 1.6)

Identical Twins

Identical twins reported being treated alike. So is it experience or genes that are accounting for their similarities?

Separated Twins More alike than fraternal twins raised

together (MTS). Identical twins share the same womb

(that’s environmental) and crucial to brain development. While the IQ’s of identical twins are more similar, the IQ’s of fraternal twins are more similar than siblings even though they are genetically no more similar.

Adoption Studies

Why are children in the same family so different? Genes? Peer influence? Birth order? Life events?

Adoption studies Compared adopted kids with biological

and adopted parents

Adoption Studies

Findings? People who grow up together,

whether biologically related to not, do not much resemble each other in personality

Adopted children have traits more like there biological parents than there adoptive parents

Adoption Studies

So does adoptive parenting matter? Attitudes, values , manners, faith, politics

as identical as identical twins. In adoptive homes, less neglect, abuse,

divorce. They score higher than biological parents

on IQ tests. Fewer problems than the children of

mothers who changed their mind about adoption.

Temperament Studies Examining how emotionally excitable an

infant is ‘Easy’ babies are cheerful, relaxed & predictable ‘Difficult’ babies are more irritable, intense &

unpredictable Temperament is mostly stable and mostly based

on heredity Earlier temperament predicts later temperament and

behavior Identical twins have more similar temperaments than

fraternal twins

Assignment Handout 3-5

Find someone you don’t know at lunch today and complete the questionnaire.

Be prepared to discuss your findings.

Nature vs. nurture? The environment has very little effect

on personality development But that doesn’t mean that your parents

don’t effect you at all Their influence can be seen in your attitudes,

values, manners, religion, and politics Most behaviors/traits are an interaction of your genes and the environment

Environmental Influence Should we really blame the parents?

NO in the environmental sense and YES in the genetic sense

Experience and brain development Use it or lose it, especially early on

Peer influence Parents are necessary for early childhood

survival – peers are necessary for lifelong survival

Peers are who we play with, work with, and eventually mate with

Environmental Influence

Genetic differences account for about half of our person-person differences in personality. What accounts for the rest? Parental nurture? Prenatal nutrition? Early stimulation? Peer influences? Culture?

Parental Influence Recall, shared environmental influences

account for less than 10% of children’s personality differences

What matters is how parents respond to a child’s genetically influenced characteristics (the “relationship-code” as termed by Reiss). The aggressive, fearless and impulsive boy

(criminal or astronaut?)

Parental Influence Recall, shared environmental influences

account for less than 10% of children’s personality differences

What matters is how parents respond to a child’s genetically influenced characteristics (the “relationship-code” as termed by Reiss). The aggressive, fearless and impulsive boy

(criminal or astronaut?)

Pre-natal Influence

Embryos receive different nutrition and varying exposure to toxic agents

Shared placentas (2/3 of identical twins) do not translate into equal blood supply. One twin can be “greedy” or be better positioned.

Early research is indicated that twins in separate placentas are less similar than twins in the same placenta

Experience & Brain Development

Studies with rats in impoverished environments.

Studies with string musicians show larger and more complex neurons.

Critical period for learning language.

What has been the most important influence in your life?

Peer Influence

As the child ages, parental influence decreases and peer influence takes over. Preschoolers will eat food with friends they

don’t eat at home Immigrant children lose parent culture if

placed with a peer group of nonimmigrants Teens who smoke have friends who smoke

Selection Effect: we seek out peers with similar attitudes and interests

Check out:

http://home.att.net/~xchar/tna/

For information on peer influence

Peer Influence

Cultural Influence Culture

The behaviors, ideas, attitudes, and traditions shared by a large group of people

Norms: the rules for accepted and expected behavior (based on group membership)

Regardless of the cultural norms of a group, most are very successful at raising children

One important consideration is that while there are significant cultural differences present, we are still more alike than we are different

Gender – Biologically Speaking

Until the 7th week of pregnancy, all babies are female It’s the activation of testosterone in a fetus

that has the XY pair of chromosomes that triggers male organ production

In the fourth & fifth months, different brain patterns develop due to different levels of testosterone and ovarian hormones

Gender – Socially Speaking

Gender roles The expectations about how men and

women behave In nomadic cultures, there is minimal

gender role occurrence Boys and girls experience the same upbringing

In agricultural societies (of which ours originated), there are strict gender role structures in place

Most of our gender identity is acquired through social learning

Gender Roles

What pressure (if any) do you feel to conform to gender roles?

Conclusion “To what extent to biology and

society determine gender roles?” Make some point form notes on the

following video to discuss next class (watching this video at school is best). Go to the Annenberg site on the blog

and watch “#17 Sex and Gender” or “youtube” it.