Methodology (Biological)

Correlations

• Correlations looks for a relationship between 2 variables. Doesn't establish a cause and effect.
• E.g. correlation between high levels of testosterone and aggression - doesn't suggest testosterone causes aggression just that there is a relationship
• Correlations don't use an IV or a DV. They use Co-Variables.
• Co-Variable: those characteristics which will be measured in a correlation.
• Correlations are shown on scatter graphs. Correlation co-efficients tell us about the strength of the relationship. A co-efficient of +1 is a perfect positive correlation, -1 a perfect negative correlation and 0 no correlation.

Correlations Evaluation

• Strengths:
• Shows a relationship between 2 co-variables
• No IV - can be used in situations where experimentation would be impossible or unethical
• In some cases strong significant correlations can suggest ideas for an experiment to determine cause and effect relationships
• Weaknesses:
• Can't establish cause and effect
• Technique is subject to any problems associated with the method used for data collection (e.g. self-report or observations may have been used to measure variables)

Spearman's Rho

• 
• Data: Interval/Ordinal (only use for correlations)
• Rank the scores for both variables
• Work out the difference between the 2 rankings for each ppt (d)
• Square the difference for each ppt (d2)
• Add up the d2 scores
• Substitute into formula and calculate the correlation co-efficient

Brain Scans

• Brain imaging techniques allow doctors and researchers to view activity or problems within the human brain, without invasive neurosurgery.
• There are a number of accepted, safe imaging techniques in use today in research facilities and hospitals throughout the world.

fMRI

• Functional Magnetic Resonance Imaging
• Technique for measuring brain activity
• It detects changes in blood oxygenation and flow that occur in response to neural activity - when a brain area is more active it consumes more oxygen and to meet this increased demand, blood flow increases to the area
• Can be used to produce activation maps showing which parts of the brain are active during a particular mental process

fMRI

• Strengths:
• High spatial resolution
• Non-invasive and no risk of radiation
• Records signals from all regions of the brain
• Produces compelling images of brain activation
• Weaknesses:
• Dispute over whether it actually measures what it claims to measure
• Very noisy - small signals and lots of noise make it difficult to pick up changes in oxygenated blood flow
• Cause and effect can't be established always - brain processes are complex and often non-localised
• Statistical methods may produce false positives

PET - Positron Emission Tomography

• Uses trace amounts of short-lived radioactive material to map functional processes in the brain
• When the radioactive material undergoes decay, a positron is emitted which can be picked up by a detector
• Areas of high radioactivity are associated with brain activity
• Mainly medical uses - checking stroke damage
• Can be used to research how the brain works by comparing the brains of those with S/Z to the brains of normal individuals
• Raine et al (1997) used PET scans

PET

• Strengths:
• Valid - the scan measures what it claims to measure
• Reliable - can be repeated and consistent results found
• Can diagnose epilepsy, alzheimers and dementia
• Show problems at a cellular level - can distinguish between cancerous and non-cancerous tumours
• Weaknesses:
• Radioactive tracer is invasive so there are ethical issues - can cause harm
• Scan itself is claustrophobic - it must be carefully explained to the individual
• Expensive
• Difficult to isolate different brain functioning precisely - non-localised

CAT/CT - Computed (assisted) Tomography

• Builds up a picture of the brain based on the differential absorption of X-rays
• The subject lies on a table that slides in and out of a hollow, cylindrical tube
• An X-ray source rides on a ring around the inside of the tube, with its beam aimed at the subject's head
• After passing through the head, the beam is sampled by one of the many detectors that line the machine's circumference
• Images made using X-rays depend on the absorption of the beam by the tissue it passes through
• Bone and hard tissue absorb X-rays well, air and water absorb very little and soft tissue is somewhere in between
• CT scans reveal the gross features of the brain very well but don't resolve its structure well

CT/CAT

• Strengths:
• Less harmful than PET scans
• Useful in looking for tumours
• Not painful and usually non-invasive (see last weakness)
• Can detect changes in physical structure to quite a good level
• Weaknesses:
• Involves X-rays which can cause cancer - sparingly used and not recommended for studying the brain
• Doesn't show areas of brain activity - just physical structures
• MRI gives clearer pictures
• May require the use of a dye to enhance the image - dye would need to be injected