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Nature and Nurture in Development

19 September 2012

Peter Baggetta

on 21 August 2015

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Transcript of Nature and Nurture in Development

In Development
1. Examine and analyze differing viewpoints on the degree of influence of nature and nurture.

2. Understand approaches to studying genetic and environmental differences.

3. Understand the process through which genes and environment interact and correlate.
Genetic and
Environmental Influences
Twins - identical vs fraternal raised

Adoption - biological vs adopted parents

Family - complex families
Types of Studies:
varying degrees of a trait present
larger correlation - closer the resemblance
estimate the contributions to individual differences from:
shared environmental influences
nonshared environmental influences - unique to the individual
How does nature and nurture work together?
Gene-Environment Relationships
Effect of genes dependent on environment and how respond dependent on genes
Ehrlich & Feldman (2003)
Marcus (2004)
Does the cultural environment influence
lifespan development more than our genes?
1. Does it make sense that the human brain would be programmed in different ways for men and women, who do, on average, show clear developmental differences?

2. Do studies that show identical twins to be more alike than fraternal (nonidentical) twins provide convincing evidence of genetic dominance? Why or why not?

3. Marcus suggests that understanding genetic influences on development requires appreciating the complexity of how genes work. Is it possible that the complexity will make it too difficult to analyze?

4. Much of the evidence for this debate comes from nonhuman animal research. How much can we learn about the nature and nurture of human development from experiment on other species?
Too few genes to explain all of the complexity in human development

Significant historical variation in what is considered "normal" behavior for each gender

Focusing on genetic causes has led to horrible social policies
Genes do not influence behavior individually, but rather through nearly infinite combinations

Small genetic differences in animals create large differences in behavior patterns

Even though brain is plastic, the changes are constrained by
genetic limits
Is there common ground?
Both genes and environment matter

Question is about:
the relative degree of influence
what is the right balance between the two
how does the balance happen during the lifespan development
Shared Species Heredity
Cultural Evolution
Modern Evolutionary Perspectives of Human Development
evolved through natural selection
genetic endowment that members of a species have in common
reason for universal patterns of development
e.g. walk and talk around 1 year of age, puberty
inherit a characteristically human environment and learn methods of adapting to the environment

based on learning and socialization

works much more quickly than biological evolution
Translation and Expression of Genetic Code
Findings from Behavioral Genetics Research
Heritability of Different Traits
Correlations highest in identical twins = .86/.72

Heritability of IQ is about .50

Genetic endowment appears to gain importance from infancy to adulthood

Shared environmental differences become less significant with age
Concordance Rates
measure of the magnitude of genetic influence on individual differences

between 0 and 1
Statistical calculations to estimate presence of the same trait in both members of a pair of twins

if concordance rates higher for more genetically related than for less = heritable trait

e.g. Homosexuality:
52% identical
22% fraternal
Genes: are identical twins more similar than fraternal twins?
Shared environment: are twins who grow up together more similar than twins raised apart?
Nonshared environment: are identical twins raised in the same home dissimilar, despite sharing 100% of their genes and the same environment?
Temperament and Personality
Buss and Plomin (1984) reported average correlations of .50 - .60 of temperament scores of identical twins but scores for fraternal twins not much greater than zero

Conclusion: living in the same home does not generally make children more similar in personality

Shared environment influences are important but nonshared influences are more important
Concordance rate for identical twin pairs is 48% and
for fraternal twins the rate is 17%

90% of children who have one parent with schizophrenia do not develop schizophrenia

Environmental factors contribute significantly

People inherit predispositions to develop disorders,
not the disorder
Strongly heritable traits:
Physical characteristics – eye color, height, weight
Physiological functions – measured brain activity, reactions to alcohol, level of physical activity, susceptibility to certain diseases

Moderately heritable trait:
General intelligence

Less heritable traits:
Aspects of temperament and personality
Susceptibility to many psychological disorders
Complex interplay:
Genes = turn on and off thru the lifespan
Shared environmental influences = strongest early in life
Nonshared environmental influences = greater as move out of the home
Ehrlich & Feldman:
gene direct blueprint
genes expressed differently - time and context
multiple and variable gene interactions
path from gene to brain to behavior complex and variable (epigenesis)
View Points:
20th Century:
genetic makeup a person inherits
sum total of all genes
+ Environment
+ Interaction
= Phenotype
the end product or result of gene expression
the characteristics or traits that are expressed
highly dynamic and context-sensitive
Yes - 0.37 is greater than 0.17, and 0.33 is greater than 0.09 = greater genetic similarity associated with greater emotional stability
Only a small effect is evident, 0.37 just slightly greater than 0.33 and 0.17 just slightly greater than 0.09
Yes - correlation of 0.37 far less than a perfect correlation of +1.0, suggesting a good deal of nonshared environmental influence
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