Methodologies

• What are CAT scans?

  • Uses structural neuroimaging
  • A series of x-ray scans from different locations around the head
  • X-rays pass through tissue of different densities at different rates
  • Images are combined to create a structure of the brain
  • Low resolution image but can visualise major structural changes
  • High contrast dye can be injected to highlight different areas of the brain
• What are structural MRI scans?

  • Uses structural neuroimaging
  • Uses detection of radio frequency signals produced by displaced radio waves in a magnetic field. It provides an anatomical view of the brain
  • Hydrogen atoms in the brain respond to the magnetic field by emitting energy
  • MRI machines use the energy signals to construct an image
• What are functional MRI scans?

  • Uses functional neuroimaging
  • Measures blood flow in the brain when a person performs a task
  • Works on the premise that neurons in the brain that are most active during a task use the most energy
• What are PET scans?

  • Uses functional neuroimaging
  • Radioactive material is injected/inhaled and flows through the bloodstream to the brain
  • Oxygen and glucose accumulate in areas of the brain which are active
  • The use of glucose breaks down radioactive materials which gives off a neutron and a positron
  • The positron hits an electron which then releases gamma rays
  • These gamma rays are detected to identify the brain activity
• What are longitudinal studies?

  A prospective observational study conducted over a set period of time where data is collected periodically.
• What are the features of a longitudinal study?

  • Often a repeated measures design where participants are assessed on two or more occasions as they get older
  • Not all longitudinal studies are experimental
  • Sample may be of all the same age/starting an activity at the same time
  • Data is taken over several test points, including at the start (baseline data) and at the end (final test point)
  • These tests could be observations, interviews etc
  • EXAMPLE: Kohlberg's study of moral development
• What are cross-sectional studies?

  Studies which compare different population groups at the same point in time.
• What are the features of a cross=sectional study?

  • Like a snapshot of behaviour
  • One group of participants representing one section of society are compared with participants from another group
  • This study may use several groups of participants who are at different points in time e.g. a group just starting therapy and a group who are halfway through therapy
• What are the advantages of using brain scans?

  • Reliability - uses scientific material, higher accuracy
  • Qualitative data - uses structural and functional neuroimaging, more detail and better quality
  • Researcher bias - no possibility for researcher bias as they have little involvement in the actual brain scan
  • Control of variables - laboratory environment, easier to control extraneous and confounding variables
• What are the disadvantages of brain scans?

  • Ethics - risk of harm to participants, may be a stress inducing process with potential discomfort
  • Cause and effect - cannot prove any correlation or find any causation of brain differences
  • Practicality - long process with expensive equipment
  • Internal validity - only uses either structural or functional neuroimaging, not possible to have rich detail for both
• What are the advantages of longitudinal studies?

  • Internal reliability - same method of data collection is used for each participant, standardised procedures prevents individual differences
  • Internal validity - prospective study provides rich detail, case studies are also often used in longitudinal studies
  • Cause and effect - prospective study allows cause and effect to be established better
• What are the disadvantages of longitudinal studies?

  • Control of variables - prospective study, difficult to control variables over several occasions
  • Researcher bias - researcher has a lot of control and influence of the study
  • Sample size - difficult to assess a large number of participants over several occasions
• What are the advantages of cross-sectional studies?

  • Sample size - highly representative as multiple groups of society are compared, increases population validity
  • Replicability - cross-sectional studies are easy to repeat to assess trends over time, increases external reliability
  • Practicality - results are obtained quickly because participants already have the condition or attribute being studied at the time of data collection
• What are the disadvantages of cross-sectional studies?

  • Sample method - similar to independent groups design, risks individual differences between groups
  • Cause and effect - difficult to establish cause and effect as they are only a snapshot in time, doesn't include what happens before and after the snapshot
  • Sample - can be difficult to gauge a sample which is entirely representative of the population group as a whole