Genetic & Environmental Influences on Behavior Nature vs. Nurture

The Nature Argument (is sometimes compelling) This guy will never be….This guy!!! Why does Brad Pitt look the way he does?

Other Big Issues in Psychology Rationality vs. Irrationality. Stability vs. Change.

Behavior Genetics The school of thought that focuses on how much our genes and our environment influence our individual differences.

Genes: Our Biological Blueprint

Genes: Know Their Location and Composition In the nucleus of every cell we have 46 chromosomes……

Except…

Chromosome Breakdown Chromosomes (Books) DNA (Pages) Genes (Words) Nucleotides (Letters)

What do we get from our parents? We inherit one set of 23 chromosomes from each parent. The two sets form pairs that contain alternate genes for the same traits. Sometimes, one gene is dominant and “overrides” the recessive gene.

Some Dominant Traits Curly hair. Unattached earlobes. Farsightedness.

Genetic Diversity The best source of genetic diversity comes from genetic mutations and new gene combinations produced at each human conception. A mutation is a random error in gene replication that leads to a change.

Chromosomal Abnormalities Gender comes from 23 rd pair of chromosomes…men have XY…woman have XX. Turner’s syndrome is single X. Klinefelter’s syndrome is extra X…XXY Down syndrome….extra chromosome on 21 st pair.

Genetic Similarities Mrs. Stout is 96% 99.9%

Identical Twin Studies Best way to really study genetics because they come from the same zygote. Bouchard Study..69 Correlation coefficient for IQ tests of identical twins raised apart..88 raised together.

What are the different types of twins? Identical (Monozygotic / from one egg) and Fraternal (Dizygotic / from two eggs).

Twin Studies: The Results To summarize the countless amount of studies: Twins (especially identical), whether or not they are raised in the same environment are very much alike in many ways. Which supports the nature side of the nature vs. nurture debate.

Heritability The degree to which traits are inherited. It is a mathematical formula. Ranges from 1 (all variance due to heredity - like tongue curling) to 0 (none due to heredity – like speaking English). As environments become more similar, heredity as a source of differences becomes more important.

Temperament A person’s characteristic emotional reactivity and intensity. It remains relatively stable over time.

Adoption Studies Adoption studies also support the nature side of the debate. Adopted children share more personality trait similarities with their biological parents than with their adoptive parents. Adoption studies also show that parenting plays a vital role in the development of belief systems.

Environmental Influences on Behavior

Types of Environmental Influences ParentsPrenatalExperience Peer InfluenceCultureGender

How Much Credit (or Blame) Do Parents Deserve? Are children clay to be molded by their parents? You and your siblings grow up in the same environment, are you all the same? Parents effect your belief systems and values much more than your personality (only about 10% of our personality differences). Parents take too much credit for success and too much blame for failures.

Prenatal Environment Lets look at perhaps our first environmental influence….

Placental Arrangements in Identical Twins: 2/3 share the same placenta.

Experience and Brain Development Parents spend a lot of $$$ sending kids to pre-school. They just play with a lot of toys. The parents could use that $$$ for a big flat screen TV. Is it money well spent?

Brain cells in an impoverished environment = smaller brains & less developed cortexes.

Brain cells in an enriched environment More well developed brains

What does this mean for humans? 6 th graders who were given stimulating care as infants scored higher on intelligence tests than those who didn’t receive that kind of care. Use it or lose it!

Peer Influence Perhaps the biggest environmental influence, at least by your age may be…. Teens are more likely to smoke because their peers smoke rather than their parents smoking. Parents are more important when it comes to education, discipline and responsibility.

Culture Behaviors, attitudes, traditions, etc… of a large group that have been passed down from one generation to the next.

What Culture Isn’t Nationality is NOT culture. Many nations have multiple, coexisting cultures. Race is NOT culture. Two people of the same race can be from different or similar cultures. Your culture is a set of beliefs and behaviors you learned from people in your environment.

Cultural Variations It is important to recognize our cultural norms: an understood rule for acceptable behavior. Individualistic vs. Collectivistic Cultures. Individualism promotes independent selves. Collectivism encourages the development of the interdependent self. Cultural differences appear in things like punctuality, personal space, show of emotions, etc.

Factors Influencing Culture Development and Diversity Population density – higher population requires more rules for maintaining order. Climate – lifestyles adapt to climate. Resources – scarcity or abundance of resources influence how people work. Technology – also influences the way people work in a society.

Cultural Research Cross-cultural research – tests hypotheses on many groups of people to see if principles apply across cultures. Some psychological principles are universal (i.e. language to communicate). Some are culture-specific (found only in some cultures).

Culture and Personality Internal Locus of Control (control their own fate). External Locus of Control (outside forces determine what happens to you). Western nations are more likely to have an internal locus of control than Asian or African nations.

Culture and Attachment In the U.S. we value a “secure attachment.” In Germany, this is often seen as being “spoiled.” Some African tribes often spend much time away from their infants (left to be cared for by others in the tribe).

Ethnocentrism The tendency to view the world only through your own cultural filters. When people from other cultures behave differently from us, we often have strong negative reactions.

What Do We Mean By Gender Differences?

Gender Matters Are there significant physical or social differences between boys and girls?

Gender We already know the nature differences. XX vs. XY But that focuses on SEX. Gender refers to our definition of male and female, based on socially and culturally influenced characteristics, as well as biology.

Physical Differences Females: Larger pelvis. Brain receives 15% more blood. 10% shorter than males. Males: Heavier bones. Greater grip strength. Proportionately larger hearts, lungs.

Physical Differences Females: Longer life expectancy. Twice the body fat. Fewer genetic defects. Males: Twice the risk of coronary disease. Higher levels of stress hormones.

More Gender Differences Females: More fearful. More verbally aggressive. More social perception. Greater empathy. Males: More active. More physically aggressive. More competitive. Greater throwing accuracy.

Differences in Throwing Ability

Social Differences Girls tend to play in a small group or with a single friend. Boys are often more involve in a large group with a more competitive focus. Men are more likely to use conversations to solve problems, while women explore relationships in conversation.

Gender Roles A set of expected behaviors for males and females. It’s a result of culture, not genetics. What gender role is she breaking?

Changing Attitudes about Gender Roles

Gender Identity Our own sense of male or female. Personalized to us. We realize our gender identity through gender-typing: the acquisition of a traditional masculine or feminine role.

Two Theories of Gender-typing

Social Learning Theory I play baseball. Son imitates my behavior.I reward son. My wife puts on makeup. My son copies her.I punish my son.

Gender Schema Theory Schema: a concept or framework of how we organize information. We develop schemas for gender which becomes the lens through which you view your experiences. That concept then influences your perceptions and behavior. Boy’s don’t do this, that’s for girls. Yeah, that’s cool!!!! I want to do that.

How and why do men and women differ sexually?

Of course, there are other differences….

Men, Women and Sex Casual sex is more accepted by men. When average men and women randomly ask strangers for sex tonight, 75% of men agreed, almost no women agreed. WHY?

Sperm is Cheap Eggs are not

What do men and women want when selecting a mate? Men want: Attractive Character Intelligence Personality Women want: Wealth Ambition Character Intelligence

Can this change?