1. Methodology of the Biological approach
L.O. To understand the use of adoption and twin studies in the Biological Approach

2. Biological approach Three types of methodology Animal experiments
Twin studies
Scans

3. Twin studies

4. Twin Studies What are the two types of twins? How are they formed?
Monozygotic Dizygotic

5. Concordance rate
Psychologists look at twins to see what traits they share by looking at concordance rates (the likelihood that, if one twin has a certain trait, the other twin will have the same trait).
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

6. What does this show us? Twin Type Concordance for schizophrenia MZs 48
DZs 17
Concordance rates for identical and fraternal twins, Gottesman (1991)

7. 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 2 sentences.

8. Twin Studies
Psychologists use twin studies to compare the effects of Nature/Genetics v Nurture/Experience.
MZ and DZ twin pairs are used to see if behaviours are shared by those who are genetically similar.
What would the results show us?

9. Twin Study example
Bouchard and McGue (1981) studied the inheritance of IQ by measuring and comparing the concordance rate (similarity) of Monozygotic (identical) twins.
After 30 studies, they found the concordance rate averaged at 86%, suggesting that a large part of intelligences seems to be inherited.
Research has found that the concordance rate in Dizygotic (non- identical) twins averaged at 60%- the same as any two siblings.

10. Twin Study Strengths Weakness
Produced a great deal of data to support biological arguments for causes of mental health problems enabling psychologists to find biological ways of helping people.
Strength: Identical twins share 100% of their genes and make perfect participants for studying genes affecting behaviour.
Weakness
Monozygotic twins are rarely separated from birth and raised in a totally different environment. This is really what is required to make the claims of the researchers truly valid.
Weakness: Concordance rates should be handled with caution as its difficult to untangle the relative effects of genetics v environment-especially if twins are reared in the same settings.
Mz twins reared together probably share a more similar rearing than Dz twins reared together. (eg if you are not as good looking or charming as your non identical twin then your life and psychological development could be very different indeed)

11. Adoption Studies Why study children who have been adopted?
Another way of looking nature/nurture.
Adoptive children share no genes with their adoptive families but share the environment.
Also share 50% with biological parents, but no longer share environment.
What would the results show us?

12. Adoption studies Strengths Weakness
Adoption studies are a very powerful resource supporting the biological view because you have isolated the environmental factors. If a biological mother has had no contact with the baby since birth and still matches I.Q. more than the adoptive mother this is powerful evidence that genes are more important than environment.
Weakness
Selective placement is a problem. Babies tend to be matched with a similar background to the one of the natural parents.
Adopted children are not representative of all children. If an adoptive child has a lower I.Q. than the adoptive mother and matches the birth mother more in this respect it maybe that the trauma of adoption has lowered the child’s IQ not genetic factors. (Obviously this would only be the case if birth mother was lower than adoptive mother).