maguire (2000)- taxi drivers

Question 1

research method

Answer 1

This was a quasi/natural experiment because the independent variable (IV) – whether the participant was a London taxi driver or a person who
did not drive taxis – was naturally varying and so could not be manipulated or controlled by the researchers. The dependent variable (DV) was
the volume of the hippocampi including their anterior, body and posterior regions; measured by analysing MRI scans of participants’ brain using
the two techniques of VBM and pixel counting.
• The study used an independent measures, matched participants design

Question 2

sample

Answer 2

The experimental group of 16 taxi drivers were all healthy, right-handed, male London taxi drivers, mean age 44 years (range 32-62 years), mean
time as a licensed London taxi driver (passed The Knowledge) 14.3 years (range 1.5-42 years).
• The control group who did not drive taxis (50 for the VBM analysis, 16 for the pixel counting) were matched for health, handedness, sex, mean
age and age range.

Question 3

outline- procedure

Answer 3

The scans of the control group were selected from the structural MRI scan data base at the same unit where the taxi drivers were scanned.
• The MRI scans of all participants were analysed using:
(i) VBM (voxel-based morphometry) which is an automatic procedure that ‘normalises’ the scans to a template to eliminate overall brain size
as a variable and then identifies differences in grey matter density in different regions of the brain. The brains of the 16 taxi drivers were
compared to those of 50 non-taxi drivers to see if there were any differences in structure.
(ii) Pixel counting compared the volume of anterior, body and posterior cross-sections of the taxi drivers’ hippocampi
with those of a previously age, gender and handedness-matched sample of 16 controls taken from the 50 used in the
VBM analysis. The images were analysed by one person experienced in the technique and blinded to whether the scan
was of a taxi driver or a control and the VBM findings. This procedure allowed the total hippocampal volume to be
calculated.

Question 4

conclusions

Answer 4

There are regionally specific structural differences between the hippocampi of licensed London taxi drivers compared to those who do not
drive London taxis.
• The professional dependence on navigational skills in licensed London taxi drivers is associated with a relative redistribution of grey matter in
the hippocampus.
• It can be suggested that the changes in the arrangement of hippocampal grey matter are acquired i.e. due to nurture.
• Findings also indicate the possibility of local plasticity in the structure of a normal human brain which allows it to adapt in response to
prolonged environmental stimuli.