These are notes on the research methods section of psy2014s, covering the behavioural, causal and correlational methods of studying the brain. (E.g., PET scans)
Research methods
Methods of studying the brain
1. Behavioural
- Measuring directly observable behaviour
2. Correlational
- Reveal a pattern of brain activity that accompanies cognitive functioning
3. Causal
- Establishing cause-effect relationships. Strongest evidence.
Each method has limitations and can lead to different interpretations. It is thus important to use different
methods to see a comprehensive picture and get robust and conclusive findings.
Converging evidence: different methodologies leading to the same conclusions. Strengths compensate for
weaknesses.
Studying how brain regions are associated with different functions (localisation):
• Single dissociation
• Damage to brain Area 1 results in Function A being disrupted but Function B is intact
• Double dissociation
• Golden standard – strongest evidence (Broca and Wernicke’s area)
• Find that damage to Area 2 leaves Function A intact but Function B is disrupted
• Existence of two distinct processes
• Association
• Damage to brain Area 3 results in disruptions of Function C & D
• Common representations/processes affected
Behavioural methods to studying the brain
• Inferring brain function from observable responses
• Limitations of behavioural experiments designed to measure:
1. Accuracy
o Ceiling/Floor effects (everyone gets everything correct or incorrect – is the outcome because of a
faulty measure or the actual thing you are studying) and
o Speed-accuracy trade-off
2. Response time
o Task difficulty (the harder a task is, the longer you think before responding – if too hard can cause
slower responses than realistic)
3. Judgements
o Dishonest or don’t know how to use scale
, 4. Protocols
Strengths: test specific theories based on predictions
Weaknesses: experimental expectancy effects, task demands and no localisation or understanding of
mechanism (go through last years notes on)
Correlational Neural methods to studying the brain
• Correlate location of brain activity with changes in function/behaviour
• Correlation does not imply causation!!!
• Helps to localise mental activity
• Data can be used to establish dissociations / associations
General limitations:
1. Doesn’t show specific brain areas
2. Brain areas may be activated because they are connected
3. Brain regions may be very close and therefore not differentiated
4 primary principles on which correlational neural methods are assessed
1. Spatial resolution
Precision in localising brain area that produces a signal/activity
2. Temporal resolution
Precision in tracking changes in brain activity over time
3. Invasiveness
Degree of introducing foreign substances into the brain
4. Cost (Equipment)
• Some use electromagnetic recording methods
• Measuring summed electrical activity of neurons
• Accurate measure of activity
• Best temporal resolution (no lag btwn what happens in brain and what is shown)
Correlational Neural Methods: The EEG
• Electroencephalography (EEG)
• Metal electrodes placed on the scalp
• Records summed electrical activity of the brain surface (specifically the cortex)
• Monitors changes over time
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