Developmental Psychology - the scientific study of how and ...



Hereditary Influences on Development

Genotype - the entire genetic makeup of a given person

Phenotype - all the genetic traits that are expressed in a person

A variety of phenotypes are possible

for each genotype.

Alcoholism

There is evidence that alcoholism has a genetic component:

- some ethnic groups have a higher proportion of alcoholics

- some people react to alcohol in ways that discourage drinking

Alcoholism is not simply a biochemical reaction:

- if the culture promotes drinking, alcoholism is more likely

- if the culture discourages or prohibits drinking, alcoholism is less likely

- alcoholism is most likely to develop between the ages of 15 and 25

alcoholism is not inevitable, whatever the genotype

Schizophrenia

Mortensen (1999) - study involved 2 million Danes born between 1935 and 1978

10% of people who had a close relative with schizophrenia themselves had the disorder

Other risk factors:

1. birth month 2. place of birth

What does the genotype set?

Canalization - when the developmental outcomes for a phenotype are restricted to a small number of outcomes, e.g., babbling in infancy

Reaction Range - the upper and lower limits of an attribute in the phenotype, set by the genotype

Examples:

- physical changes at adolescence

- graying at ...

- IQ

Heritability - the trait variability in a population that is determined by variations in genetic inheritance

Heritability measurements take into account both genetic and environmental factors.

- if a genetically similar population shows marked individual differences, they must be the result of environmental factors

- if a population within a similar environment shows marked individual differences, they must be the result of genetic factors

Genotype/Environment Interaction

Scarr (1992) - the genetic uniqueness of individuals results in the creation of unique environmental experiences

Passive genotype/environment correlation

- musical parents may both pass on their musical genes and provide a home environment that is rich in musical experiences

Evocative genotype/environment correlation

- genetically influenced attributes may affect others' responses: a cranky baby or a non-responsive baby may discourage playful interaction

Active genotype/environment correlation

- children choose environments that are compatible with their predispositions: sociable children are likely to search out companionship

Genetic differences become more influential across development as individuals mature and do their own "niche-picking."

Shared environmental influences - experiences that individuals living in the same home share, e.g., parental interests, church attendance,

Non-shared environmental influences - experiences that individuals living in the same home do not share, e.g., sibling relationships, family income (over time)

- the impact of genotype may lead to microenvironments, environmental characteristics that are specific to a child

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