Methodology of the Biological approach

TWIN STUDIES

Biological approach

• Two types of methodology– Animal experiments– Twin studies

Twin Studies• What are the two types of twins?• How are they formed?

Monozygotic Dizygotic

Example of a Twin Study

• Bouchard and McGue (1981)• Studied the inheritance of IQ– What is IQ?

• They compared the IQ scores of different types of twins who were reared together and separately. They were looking for the genetic basis of IQ by using concordance rates

Bouchard and McGue (1981)

• Concordance rate– A score from 0-100%– The higher the concordance, the more similar the

two scores are• E.g. 100% would be identical scores• 0% would be completely unrelated• See Pg 13

Bouchard and McGue (1981)RELATIONSHIP IQ TEST CORRELATION

86%

72%

60%

Bouchard and McGue (1981)

• What can we conclude from these results about the effect of genes on IQ?

Twin studies

• Why are twin studies used in the biological approach?– Think about the assumptions of the approach

• With a partner, come up with an answer to this question that is no longer than 3 sentences

What do we know now?

• MZ TWINS are Identical. T or F?• What is a concordance rate?• What kind of twins have 72% concordance for

IQ?• Why use twins studies in the biological

approach?• Key weakness of Twin studies?