Longitudinal and cross-section studies, and brain scans Flashcards
Longitudinal study - definition
A study conducted over a long period of time.
Often a form of repeated measures design in which participants are assessed on two or more occasions as they get older.
Some longitudinal research is not experimental, people may simply be observed for a number of years.
Longitudinal - advantage
Participant variables are controlled.
This is because longitudinal studies often use a repeated measures design.
Longitudinal study - disadvantage
Attrition is a problem.
Some of the participants inevitably drop out over the course of a study.
This leaves a biased sample.
Participants are likely to become aware of the research aims.
Cross-sectional study - definition
One group of participants representing one section of society are compared with participants from another group.
Example:
Young people compared with old people.
Cross-sectional study - advantage
Quick.
Can be conducted in less than a year.
Cross-sectional study - disadvantages
The groups of participants may differ in more ways than the behaviour being researched.
Cohort effects occur.
This is because a group of people who are all the same age share certain experiences.
Brain scans - definition
A technique used to investigate the functioning of the brain by taking images of the living brain.
CAT scans - key points
Involves taking a series of x-rays and combining them to form a comprehensive two-or-three dimensional picture of the area being scanned.
Usually a dye is injected into the patient as a contrast material and then they are placed in the cylindrical CAT scan machine.
CAT scans - name of study
Johnstone et al
CAT scans - Johnstone et al
Used CAT scans to show that the brains of people with schizophrenia were different to normal brains.
The fluid-filled spaces in the brain (ventricles) were much larger.
CAT scans - advantages
Useful for revealing abnormal structures in the brain such as tumours, or structural damage.
The quality of the images is much higher than that of x-rays.
CAT scans - disadvantage
Require more radiation than traditional x-rays.
The more detailed and complex the CAT scan is, the more radiation exposure the patient receives.
CAT scans only provide structural information.
MRI scans - key points
Involves the use of a magnetic field that causes the atoms of the brain to change their alignment when the magnet is on and emits various radio signals when the magnet is turned off.
A detector reads the signals and uses them to map the structure of the brain.
MRI scans - name of study
Maguire et al
MRI scans - Maguire et al
Used MRI scans to demonstrate the taxi drivers had larger hippocampi than non-taxi drivers, supporting the view that this area of the brain is important in spatial memories.
Functional MRI (fMRI) - definition
Provides both anatomical and functional information by taking repeated images of the brain in action.
MRI scans - advantages
Gives a more detailed image of the soft tissue in the brain than CAT scans.
This is because it involves passing an extremely strong magnetic field through the patient rather than using x-rays.
Best suited for cases when a patient is to undergo the examination several times successively in the short term.
This is because, unlike CAT scans, it doesn’t expose the patient to the hazards of radiation.
MRI scans - disadvantages
Take a long time.
Can be uncomfortable for patients.
PET scans - key points
Scan involves administering slightly radioactive glucose to the patient.
The most active areas of the brain use glucose, and radiation detectors can “see” the radioactive areas, so building up a picture of activity in the brain.
Scans take between 10-40 minutes to complete and are painless.
PET scans - name of study
Raine et al
PET scans - Raine et al
Used PET scans to compare brain activity in murderers and normal individuals.
Found differences in areas of the brain such as the prefrontal cortex and the amygdala, regions previously associated with aggressive behaviour.
PET scans - advantages
Reveal chemical information that is not available with other imaging techniques.
Means that they can distinguish between benign and malignant tumours.
Show the brain in action.
This is useful for psychological research.
PET scans - disadvantages
Costly.
Not easily available for research.
The patient has to be injected with a radioactive substance.
This technique can only be used a few times.
Less precise than MRI scans.
