g11 EOYE Exam: Biological studies SAQ (8)

maguire

To investigate whether the brains of London taxi drivers were different due to their extensive spatial navigation experience

quasi experiment. right handed male london taxi drivers, compared with non taxi drivers. MRI VBM scans and pixel counting of hippocampal area

taxi drivers had a larger posterior hippocampus and smaller anterior hippocampus.

strength: MRI provided objective and reliable data

weakness: quasi-experiment - not causal

milner

to better understand the effects of surgery on patient HM. HM had an accident, had epilepsy, had surgery resulting in anterograde amnesia.

case study. method triangulation: overt observations, MRI, cognitive testing, interviews.

HM could not form new memories, but his LTM remained intact. he had a working memory capacity. MRI showed damage to the hippocampus

strength: Longitudinal study over 50 years

weakness: Cannot be easily replicated

ethics: informed consent

draganski

To see whether learning a new skill, juggling, would affect the brains of participants

field experiment. group of young adult non jugglers. baseline MRI. allocated to non jugglers or jugglers. once jugglers mastered a basic routine they had a second mri. jugglers stopped juggling and a third mri was taken 3 months later. measured changes in grey matter

no initial grey matter differences between groups. after mastering the skill, jugglers had increased grey matter in the mid-temporal area (visual memory). 3 months later, grey matter decreased. no changes in non jugglers.

strength: pre test

weakness: naturalistic setting may introduce confounding variables, affecting internal validity

rogers and kesner

To determine the role of acetylcholine in the formation of spatial memory.

true experiment. rats trained in a maze. randomly assigned to receive antagonist scopolamine (blocks ACh) or a saline solution as a control. rats re-ran the maze after injection and encoding and retrieval was measured by comparing the trials.

The scopolamine group made more errors and took longer to relearn the maze. Once learnt, it did not affect memory retrieval.

strength: use of placebo

weakness: reductionist approach - does not account for different types of memory

newcomer

To investigate whether high levels of cortisol interfere with verbal declarative memory.

true experiment. double blind. healthy particpants matched for age and gender. 3 conditions for 4 days: high dosage of cortisol 160mg, low dosage 40mg, placebo. participants were asked to recall a paragraph before and after

High cortisol group showed the worst memory performance. No difference between low-dose and placebo. Memory returned to normal after stopping cortisol

strengths: true experiment with baseline test

weakness: limited control over external stressors

ethics: undue stress or harm

saxton

To investigate whether androstadienone influences how attractive females rate males during speed dating.

females given a cotton wool nose plug with either: androstadienone + clove oil, clove oil only, water. participated in speed dating with 22 males.

In 2 out of 3 trials, females exposed to androstadienone rated males as more attractive than the other groups.

strength: allows for real life interactions with others

weakness: Reductionist - over-simplifies the attraction of women to men by reducing it to androstadienone

caspi M5F3

To investigate whether the 5-HTT gene interacts with stressful life events to increase risk of depression.

longitudinal quasi experiment. 800+ New Zealanders divided by allele genotype: 2 short, 1 short + 1 long, 2 long alleles. surveyed on life stress and assessed for depression between the ages of 21–26.

Participants with one or two short alleles showed more symptoms of depression after stressful events than those with two long alleles. Risk is highest with 3+ events

The 5-HTT gene may moderate the effect of stress on depression risk, supporting a gene-environment interaction model.

weissman et al M3F3

To study the potential genetic inheritance of MDD across three generations.

Longitudinal family study. 150+ grandchildren, their parents, and grandparents over 20 years. researcher triangulation: child psychiatrist and psychologist, blind to previous diagnoses, assessed psychiatric disorders.

Grandchildren with two generations of MDD had higher rates of psychiatric disorders, compared to children whose parents were not depressed

Depression may be genetically transmitted across generations.

Large sample, longitudinal data

No actual gene studied