Maguire (2000) Flashcards
What were Maguire’s 2 aims?
1) to investigate the extent of structural changes in the hippocampus of London taxi drivers as a result of extensive navigational experience
2) to see if there is a correlation between length of time of taxi driving experience and the measure of grey matter volume
What was the sample of the experimental group?
- 16 males
- licensed as black taxi drives
- 1.5-42 years experience
What are the weaknesses of the experimental sample?
- gender bias (only men = androcentric)
- culture bias (only London = ethnocentric)
- small (16) = lacks population validity - not representative or generalisable
What was the sample of the control group?
- 50 brain scans
- obtained from a database
- right handed
- 32-62 years old
- healthy
What was the sample design?
Matched Pairs
What are the strengths of the sample design?
- reduced individual differences
- reduced chance of demand characteristics and order effects
What are the weaknesses of the sample design?
individual differences still remain (not possible to completely remove)
How were participants from the experimental and control groups matched?
- health
- handedness
- sex
- age
What should be noted about one participant?
one taxi drivers data was not included in the correlational analysis as he had 42 years experience and was a clear outlier - would have skewed data
What is the test about taxi driving called?
The Knowledge
What is the premise of ‘The Knowledge’?
- intensive 2 year training course
- need to learn 25,000 streets
- general knowledge of major routes and points of interest
What is the method?
- Quasi Experiment
(+ correlation)
What makes this study a quasi?
the sample were already London black taxi drivers or not
What are strengths of a quasi experiment?
- reduced researcher bias
- ecological validity
What are the weaknesses of a quasi experiment?
- lack of control = less reliable / valid
- cannot establish causality
What is the DV?
volume of hippocampi including anterior (front); body (middle); posterior (back) regions
What is the IV?
being a taxi driver or not being a taxi driver
What are the two tests that measures the DV?
VBM and Pixel Counting
What type of scientific measure was used?
MRI scans
What is the design?
independent measures
What are strengths of the design?
- reduced chance of demand characteristics and order effects
What are the weaknesses of the design?
- individual differences
What was the purpose of the MRI scan?
- shows 2D and 3D images of brain structure and grey matter
What was used to analyse the results of the MRI?
VBM = Voxel Based Morphometry
What did the VBM produce?
3D Grey Matter in brain regions
What did Pixel Counting produce?
2D overall hippocampal volume of structures
What is VBM?
an automatic computer software that ‘normalises’ the scans to eliminate overall brain size as an extraneous variable - gives output to the size of the hippocampi
What is Pixel Counting?
image slices which are analysed by a blind researcher - counted to indicate the volume of the anterior, body, and posterior cross-sections of the hippocampi
Why is Pixel Counting a strength?
- controlled conditions
- blind researcher = objective - no researcher bias
Why is using an MRI ethical?
antiinvasive and unharmful
What were the key findings from the VBM?
- showed no significant differences between the brains of taxi drivers and controls - except for the hippocampi
- taxi drivers had significantly more grey matter volume in the right and left posterior hippocampi
- controls had more grey matter volume in the right and left anterior hippocampi
What were the key findings for Pixel Counting?
- no significant differences between overall volume of the hippocampi = no other grey matter had been removed from any other areas of the brain
- taxi drivers had significantly more volume in the left posterior hippocampi
- controls had more volume in the right anterior and body of the hippocampi
- suggests that taxi drivers have a different brain structure
What were the key findings from the correlational analysis?
- positive correlation was found between length of time as a taxi driver and posterior hippocampal volume (0.6)
- negative correlation was found between length of time as a taxi driver and anterior hippocampal volume
- indicates that the brain changes over time to meet demands of being a taxi driver
What type of data did Maguire collect?
Quantitative
What are the strengths of this type of data?
- objective
- easy to analyse and compare
What are the weaknesses of this type of data?
does not provide detailed reasoning as to the WHY behind behaviour
What were the conclusions?
- there are regionally specific structural differences between the hippocampi of London taxi drivers and controls
- there is local plasticity in the structure of the brain as it adapts in response to prolonged environmental stimuli
