With reference to relevant research studies, to what extent does genetic inheritance influence behaviour? (22)
To What Extent (22) – Consider the merits or otherwise of an argument or concept. Opinions and conclusions should be presented clearly and supported with appropriate evidence and sound argument.
Genetics on behaviour
- Monozygotic twins -> identical twins.
- 100% same genes.
- If twin A has something, twin B must have it.
- Dizygotic twin -> fraternal twins/siblings.
- 50% similar genes.
- If there is a genetic aspect to behaviour, a high concordance rate would be expected from Monozygotic twins.
- Different types of genetic studies
- Twin studies
- Family studies
- Adoption studies
Correlational study
- Genetics research mostly done through correlation study.
- Concordance rate (presence of the same trait).
- Relationship/Association.
- Show to what extent two variables are related.
Strengths of correlation studies
- Shows how closely two variables relate
- High ecological validity, natural environments
- Allow study that could not be tested through experiment ethically
- Representative sample
Weaknesses of correlation studies
- Bidirectional ambiguity: cannot tell which caused which
- No manipulation of independent variable
Procedures of correlational genetic studies
- Correlational genetic studies are all done in a similar manner.
- Observation of pairs of twins or families.
- For twin studies, both Monozygotic (MZ) and Dizygotic (DZ) twins, both reared together and apart, will be used.
- Compare concordance rate of depression through the means of percentage.
Twin studies
- If it were a wholly genetic disorder the concordance rate for MZ twins should be 100 per cent and for DZ twins 50 per cent.
- Otherwise, other factors must be involved.
Family studies
- Similarly to twin studies, if depression was caused by genetic factors, we would expect it to run in families.
- The closer you are genetically to someone in your family, the more likely you will be to have depression.
| Genetics studies grid |
| Researcher |
Research for |
# of pairs |
Subjects |
Concordance rate |
| Price |
Bipolar depression |
97 |
MZ twins |
Reared together |
68% |
| Reared apart |
67% |
| 119 |
DZ twins |
23% |
| Allen |
Unipolar depression |
- |
MZ twins |
40% |
| - |
DZ twins |
11% |
| Bertelsen, Harvald and Hauge |
Unipolar depression |
- |
MZ twins |
80% |
| - |
DZ twins |
16% |
| McGuffin et al. |
Unipolar depression |
117 |
MZ twins |
40% |
| DZ twins |
20% |
| Gershon |
Unipolar depression |
- |
First degree relative |
- Individuals with a first degree relative with depression was about two to three times higher than in the general population.
- Social learning theory might be a possible explanation.
|
| Wender |
Unipolar depression |
- |
Adopted children |
Adopted children who went on to develop depression had biological parents that were eight times more likely to have depression than their adoptive parents.
|