Psychology Sorted

Key studies are studies that are the most useful for any Psychology course, because they provide the ‘key’ to understanding a concept or theory.  For example, Maguire’s famous ‘taxi driver’ study, Loftus and Palmer’s ‘car crash’ study or Rosenhan’s research into the validity of diagnosis on admission to mental hospitals.

Teachers and students can benefit by summarising these studies according to Background, Aim, Participants, Procedure, Results, Conclusion, Evaluation.  This can be done on 1-2 sides of paper and kept to be used for essays, revision and even for HL Paper 3 practice if you are an IB Diploma teacher or student.  Below is a short example of what this could look like, from the biological approach.

KEY STUDY: Caspi et al. (2003) Influence of Life Stress on Depression: Moderation by a Polymorphism in the 5-HTT Gene.

 Background

Looked at the relation between inherited short alleles on the 5HTT serotonin transporter gene and incidences of stress and subsequent depression.

Links to:

• Abnormal Psychology: Genetic explanation for inherited predisposition to depression as a response to environmental stressors.

Aim

To investigate whether a functional change in the 5HTT gene is linked to a higher or lower risk of depression in an individual.

Participants

The researchers used an opportunity sample from a cohort of participants who were part of another longitudinal study. There were 847 participants of 26 years old and they were split into three groups, depending on the length of the alleles on their 5HTT transporter gene.

Group 1 – two short alleles

Group 2 – one short and one long allele

Group 3 – two long alleles

Procedure

1. Stressful life events occurring after the 21^st birthday and before the 26^th birthday were assessed using a life-history calendar.
2. Past-year depression was assessed using the Diagnostic Interview Schedule.
3. A correlation was tested for between stressful life events and depression, between the length of the alleles and depression and an interaction between perceived stress and the length of the alleles.
4. A further test was done to see if life events could predict an increase in depression over time among individuals with one or two short alleles.

Results

The participants with two short alleles in the 5HTT transporter gene reported more depression symptoms in response to stressful life events than either of the other two groups. Those participants with two long alleles reported fewer depression symptoms. Moreover, childhood maltreatment was predictive of depression in adulthood only in adults with either one or two short alleles.

Conclusion

While there is no direct relation between short alleles on the 5HTT gene and depression, there is a relationship between these and incidences of stress and subsequent depression. The long alleles seem to protect against suffering depression as a result of stress. The effects of the gene adaptation are dependent on environmental exposure to stress.

Evaluation of Caspi et al. (2003)

Strengths

• This was a very large cohort of males and females and the age was controlled in order to isolate the variable of number of stressful life events between the ages of 21 and 26.
• It was a natural experiment, with the naturally occurring IV being the length of the alleles. If the results are replicated this would suggest high reliability.

Limitations

• Gene action is highly complex, and actions of other genes could not be controlled. While the stressful life events were standardised as employment, financial, housing, health and relationship, whether or not a participant experienced a certain event as stressful is highly personal.
• The symptoms of depression were self-reported, although each participant was contacted in order to verify the symptoms; self-reporting can be unreliable.

Reference

Caspi, A., Sugden, K., Moffitt, T. E., Taylor, A., Craig, I. W., Harrington, H., … & Poulton, R. (2003). Influence of life stress on depression: moderation by a polymorphism in the 5-HTT gene. Science, 301(5631), pp. 386-389.