With reference to relevant research studies, to what extent does genetic inheritance influence behavior?

Types of studies done in genetics

Twin Studies
Adoption Studies
Family Studies
What is intelligence?

Overview

-Genes (genetic information in DNA passed on from parents to offspring) influence behavior indirectly: influence the production of proteins that affect anatomy and physiology of body.

-Some behaviors are more genetically influenced than others.

-There is an interaction between environmental, biological, cognitive and genetic factors in the development of behavior.



Correlation Studies (show relationship between two variables)



Thomas Bouchard’s concordance study of identical twins (1979)

Aim: to show how some behaviors run in families, regardless of environmental factors

Participants: two identical twins separated at birth and reunited at age of 39

Experiment: ask both twins questions based on actions/behavior in daily life

Results: many behaviors matched (ex. drove Chevrolets, police work, build furniture, same name for son & dog)

Conclusion: Certain components of basic personality/behaviors are inherited.



Caspi et. al. (2003)

Aim: To investigate relationship between 5-HTT gene and depression

Participants: 847 Caucasian New Zealanders

Experiment: Had participants give self-reports on depression (cross-check with their friends)

Results: People with short allele for this gene correlated with more vulnerability to depression Conclusion: Certain diseases based on behavior are caused by genes.



Lykken & Tellegen (1996)

Aim: To investigate how closely twins’ moods correlate

Participants: 3,000 identical & fraternal twins

Experiment: Collect information based on moods from both kinds of twins

Results: Identical twins, unlike fraternal twins, have similar moods regardless of whether they have been raised together or separated at birth.

Conclusion: Happiness, which plays a role in behavior, is affected by genes.



Bouchard et. al. (1990)

Aim: To investigate relationship between heredity and weight gain

Participants: 12 pairs of male identical twins

Experiment: Participants stayed in a dormitory for 100 days to gain weight (ate 4 large meals per day)

Results: Twins gained the same amount of weight in same places in the body.

Conclusion: Gaining weight, a factor which is related to behavior, can be related to genetics.



Evaluation of Studies based on Genetic Influence on Behavior

Strengths:

-Useful for understanding psychological phenomena (ex. Personality, help battle hereditary diseases, etc.)

-Based on empirical support

Limitations:

-Correlation studies show relationship but cannot infer whether it is a cause-effect behavior.

-Underestimate cognitive and socio cultural influences on behavior

-Problems with research: Problems of self report, researcher expectancies, general ability problems, validity problems etc.


Case Studies: Bouchard and McGue (1981), Shields (1962), Scarr and Weinberg (1976)
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