Longitudinal and cross-sectional studies, and brain scans

Question 1

Longitudinal studies

Answer 1

A study where research is conducted over a long period of time in order to observe long term effects e.g the difference between people of different ages

• case studies can be longitudinal e.g bowlbys 44 thieves studies children over a period of many years

Question 2

Evaluation of longitudinal studies

Answer 2

+ uses repeated measures — so the same person is tested on a number of occasions and compared which means the other variables are controlled

• attrition is a problem — some of the participants inevitably drop out over the course of a study and they are more likely to be ones who are less motivated or more unhappy which leaves a biased sample
• participants are more likely to become aware of the research aims and their behaviour may be affected
• studies can take a long time to complete which makes them more expensive
• findings may not be generalisable because of unique characteristics of the cohort

Question 3

Cross sectional study

Answer 3

One group of participants representing one section of society e.g young people or w/c people
- they are compared with participants from another group e.g old people or m/c people

Question 4

Evaluation of a cross sectional study

Answer 4

• the groups of participants may differ in more ways than behaviour being researched
  e.g if a researcher is comparing teachers, doctors and solicitors — may differ in terms of profession but also because teachers have less money
  
  • these differences are due to participant variables than the IV
• Cohort effects may occur because a group of people who are all the same age share certain experiences e.g the IQ od 20 somethings can be compared with 80 somethings and find that the latter was much lower — suggests IQ declines with age however it might be that the 80 somethings has lower IQs when they were 20 something. This is a cohort effect

+ can be relatively quick and can be conducted in less than a year and longitudinal take many years and decades

Question 5

Brain scans

Answer 5

• main focus for understanding the human behaviour is through the brain
  -in the past the only way to study the brain was through post mortem examination
• in the 1950s the only method available for studying brain activity was EEG where electrodes are placed on the scalp and electrical activity in different regions of the brain can be recorded

Question 6

The development of brain scanning techniques

Answer 6

• more precise methods of studying the brain have been developed:
  
  • CAT scans
  • MRI scans
  • PET scans

Question 7

CAT scans

Answer 7

Computed axial tomography
- these involve a series of x-rays and combining them to form a comprehensive two or three dimensional picture of the area being scanned
- a dye is injected into the patient as a contrast material and then they are placed in the cylindrical CAT scan

Question 8

Evaluation of CAT scans

Answer 8

advantage - useful for revealing abnormal structures in the brain such as tumours or structural damage
- quality is much higher than traditional X-rays

disadvantage - require more radiation than traditional x-rays and the more detail and complex then the more radiation exposure the patient receives
- only provide structural info

Question 9

MRI scans

Answer 9

Magnetic resonance imaging
- involve using a magnetic field that causes the atoms of the brain to change their alignment when the magnet is on and emit various radio signals
- a detector reads the signals and uses them to map the structure of the brain

Question 10

Evaluation of MRI scans

Answer 10

advantage - give more detailed image of the soft tissue in the brain than CAT scans
- best suited for cases when a patient is to undergo the examination several times successively in the short term whereas unlike the CAT it does not expose the patient to the hazards of radiation

disadvantage - take a long time and can be uncomfortable

Question 11

PET scans

Answer 11

Position emission tomography
- involves administering slightly radioactive glucose to the patient
- take between 10 to 40 mins to complete and are painless
- raine et al used PET scans to compare brain activity in murderers and normal individuals — found differences in areas of the brain associated with aggressive behaviour

Question 12

Evaluation for PET scans

Answer 12

advantages - reveal chemical information that is not available with other imaging techniques — can distinguish between benign and malignant tumors
- can show the brain in action qhich is useful for psychological research

disadvantage - expensive so not easily available for research
- patient has to be injected with radioactive substance which can only be used a few times
- less precise than MRI scans