1. Unit 2 Understanding the Individual
Methodology

2. You need to
Be able to describe and evaluate PET and MRI scanning techniques
Be able to describe and evaluate twin and adoption studies as research methods
Be able to describe and evaluate the use of animals in laboratory experiments including ethical and practical
issues.

3. This lesson will be about Twin and Adoption studies
Another method used by psychologists to tease out the effects of Nature and Nurture

4. Twin Studies, adoption studies and correlational analysis
contribute to our understanding
of the learnt/innate debate

5. Background
Hopefully you will have already read the first part of the ‘Brain’ text book (p ) Ideally you will already be aware of how twin and adoption studies are used as research methods.

6. Remember you can be asked about ‘Underlying Assumptions’
Identify at least 2 assumptions of the following approaches in psychology:
(meaning what is considered to be important within each particular approach)
Cognitive
Social
Psychodynamic
Biological
So, can you now identify 2 assumptions of the biological approach?
Students in groups to come up with 2 for each

7. Nature
The ‘nature’ view of psychology suggests that all behaviour is determined by hereditary factors. Genes are thought to provide the blueprint for all behaviours; some of these will be present at birth, and others are thought to be on a ‘pre-programmed’ schedule and will emerge as the individual matures.

8. Nurture
The nurture debate proposes that all human behaviour is the result of interactions with the environment. In this debate the individual is regarded as being born with no predispositions to behaviour and so everything they do is from environmental interactions. They are born like a Blank Slate

9. Watch the separated twins clip
Identify which characteristics are inherited – i.e Nature
Identify which characteristics are the product of upbringing – i.e. Nurture

10. Recap - Correlation
Correlations show relationships between 2 sets of data. (i.e. how closely they match)
A correlation coefficient is a number between
+1 and -1 expressed as a decimal . Eg +0.86
The direction of the number ie positive or negative indicates whether the relationship is positive (as one goes up the other goes up) or negative (as one goes up the other goes down)
The nearer to plus or minus one the number is shows how strong the relationship is.
When looking at twin or adoption studies we tend to look for positive relationships as it would be very strange if the closer the biological relationship the more unlike someone we were

11. Comparing
When we say we compare twins, or comparing children with parents we mean on a measurable variable and because we are psychologists this will be something to do with behaviour for example
Intelligence
Aggression
Introversion/extroversion
Sense of humour
Mental illnesses such as depression or schizophrenia
Psychologists talk about concordance rates

12. Concordance rates
Simply the correlation coefficient converted from a decimal to a percentage. A correlation coefficient of 0.79 becomes A concordance rate of 79%

13. Identical twins share 100% of their DNA
Non-identical twins share only 50% of their DNA

14. Bouchard IQ concordance rates
Dizygotic (2 eggs) Monozygotic
DZ MZ
55% concordance % concordance
MZ reared apart
76% concordance
What does this tell us about IQ?
Identical Twins

15. Twin studies
With twin studies there are 2 main methods
1.comparing concordance rates of monozygotic twins with dizygotic twins
2.Comparing monozygotic twins reared together with monozygotic twins reared apart

16. Adoption studies
With adoption studies we tend to compare the adopted child with the biological mother and the adoptive mother to see which correlation coefficient is highest
e.g.
Child and adoptive mother 0.42
Child and biological mother 0.72

17. Siblings
Sometimes but less often sibling studies will be done where the child is compared to biological and adoptive siblings

18. Problems
In general the problem is that there are so many variables that come into play when comparing families.
This is especially the case when it comes to adoption and reared apart twin studies.
This enables some level of choice in families chosen by researchers which may create a bias towards what the scientist is trying to show.
i.e. support the learnt or innate debate. Scientists are not meant to favour one outcome when doing research but in this hotly debated topic they often do.

19. Twin and adoption studies checking learning…
What are twin studies?
Explain what is meant by concordance rates.
Define MZ and DZ twins.
What is meant by the terms nature and nurture?
What are adoption studies?
What are the problems with using twin and adoptive studies?
List three further issues with twin and adoption studies.

20. Practice For each of the studies describe how you would use
a twin study
a study of twins reared apart
an adoption study
To find out if depression is inherited.
2. To investigate the nature-nurture issue.
3. To find out if IQ is inherited.

21. Answers
To look at whether depression is inherited. Find mothers diagnosed as suffering from depression and whose children have been adopted. Find the children. Check the children for signs of depression. Check the adoptive mothers for depression. If the adopted children with depressed biological mothers have depression, it +is evidence for some genetic factor causing depression, this true if the adoptive mothers do not suffer from depression.

22. So for example…
To look at the nature-nurture issue Find twins that were reared apart throughout their childhood. Check how similar the are, particularly if they have not yet met one another. Alternatively, check how similar they were when they first met as adults. If they are similar as adults, similarity is likely to be genetic.

23. For example….
To look at IQ and how far it might be inherited. Find MZ and DZ twins. Give both an IQ test. See how different the scores are between the two twins. If the scores for the MZ twins are more similar than the scores for the DZ twins, then this indicates at least some genetic cause for IQ.

24. Gottesman & Shields (1966)
This research used twin studies to investigate whether schizophrenia has a genetic basis
It is described in your Brain text book p288