Nature and Nature and Nurture in Nurture in PsychologyPsychology

Module 3:

Imagine for a moment that your adoring parents, who believe you are perfect, decide to clone you, creating a perfect genetic replica of you. Would the new baby, your identical twin, grow up to be exactly like you? What if the baby were exposed to a different prenatal environment – one polluted (or not) by drugs or viruses? What if your parents had to give the baby up for adoption or decided to move to a different part of the world?

Behavior GeneticsBehavior Genetics

School of thought that focuses on how much our genes AND our environment influence our individual differences

Importance of both genetic and environmental factors on thoughts and behavior

GenesGenesThe biochemical units of heredity that make up chromosomes

Many genes together make up chromosomes

This is a chromosome, made up of many genes.

EnvironmentEnvironmentEvery non-genetic influence, from prenatal nutrition to the people and things around us

Any influence, other than genetic, on an individual’s behavior

Include:◦Diet (healthy vs. unhealthy)◦Family/home (smokers vs. non-smokers)

◦Cultural , religious, etc. group

◦Home location (rural, urban)

Nature and Nurture Nature and Nurture DebateDebateNature = the genetic code passed from parent to child.

Nurture = all environmental influences from prenatal development on.

Genetics in Genetics in BriefBrief

ChromosomesChromosomes Found in every cell in

our body Made up of DNA (which

contain our genes) 46 pairs of

chromosomes in each cell

23 received from each parent(22 pairs of autosomes and one pair of sex chromosomes)

Female sex chromosome = XX

Male sex chromosome = XY

Cells – nucleus – chromosomes – DNA - genes

ChromosomesChromosomes

Deoxyribonucleic Acid Deoxyribonucleic Acid (DNA)(DNA)A complex molecule

containing the genetic information

The “stairs” on the DNA “ladder” are the genes

Coded (to distinguish) with the letters A, T, C or G

These individual lettered genes are called “nucleotides”

Interesting!!!!!!!!!!!!Interesting!!!!!!!!!!!!A fruit fly has about 15,000 genesA human has only about 25,00099.9% of your 4-letter DNA sequence is the same as every other human; genetically, you are nearly identical to everyone else in the worldWe are each different or unique, genetically, by approximately 0.01%

CellulaCellular r MakeuMakeupp

Cellular MakeupCellular Makeup

Cellular MakeupCellular Makeup

Gene Gene MutationMutation Errors in gene

replication that lead to a change in an individual’s genetic code

The source of genetic diversity (what separates us from the 99.9%)

Can be spontaneous or induced

Can lead to desirable or undesirable changes

70% of genetic mutations are usually harmful to an individual, the remaining 30% are neutral or mildly beneficial

For example, a butterfly may produce offspring with new mutations. The majority of these mutations will have no effect; but one might change the color of one of the butterfly's offspring, making it harder (or easier) for predators to see. If this color change is advantageous, the chance of this butterfly surviving and producing its own offspring are a little better, and over time the number of butterflies with this mutation may form a larger percentage of the population

PredispositionPredisposition

The possibility of something happening based on our genes

The environment may or may not trigger the predisposition

Example – disease (i.e. cancer)

Nature Nature and and Individual Individual DifferencDifferenceses

““But I….”But I….”Despite genetics, we, as individuals

often end up very much our own person.What accounts for each of us being

different from all others?Behavior geneticists study such

questions using twin studies and adoption studies

Identical TwinsIdentical TwinsNature’s human clonesDevelop from a single

fertilized egg that splits in two, creating two genetically identical organisms

Called monozygotic twins

Fraternal Fraternal TwinsTwinsTwins who developed from separate eggs

Genetically no more similar than other siblings, but they share a fetal environment

Called dizygotic twins

Twin Twin StudiesStudiesUsed to determine the

heritability of a given traitData is collected from both identical and fraternal twins on the trait

Compare the data between the two groups

Important not to conclude that a specific behavior is inherited

Evidence from Twin Evidence from Twin StudiesStudiesIntelligencePersonality traitsDivorce rates

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Adoption StudiesAdoption StudiesBiological parents supply the nature and adoptive parents provide the nurture

Study after study reveals that adopted children share more personality trait similarities with their biological parents than with their adoptive parents

Environmental FactorsEnvironmental FactorsEarly Brain DevelopmentPeer InfluencesCultural Influences (norms,

individualism, collectivism)

Early Brain Early Brain DevelopmentDevelopmentBrain development also impacts who we

become; our thoughts and behaviors“Experience nurtures nature”The brain processes we use in early learning do

pave the way for later learning of more complex information

If you are raised in an impoverished environment you will not develop to the same capacity as someone who was; simple.

Early experience is criticalThe brain’s pathways maintained through

practice or experience will remain strong and, and neglected pathways will fade with disuse

Peer InfluencesPeer InfluencesPeer influence in adolescence is very powerful.

Many studies suggest a peer group is correlated with school performance, smoking, and other behaviors.

CultureCultureThe shared attitudes, beliefs, norms and behaviors of a group communicated from one generation to the next