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
SEE HANDOUT
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