Maguire (2000) Navigationrelated structural changes in the
hippocampi of taxi drivers.
Maguire (2000)
• This study looks at
the brains of
London taxi drivers
and examines the
role of the
hippocampus in
helping them to
navigate their way
around the city.
Maguire (2000) What is the
hippocampus?
• Hippocampus is the
Latin name for
seahorse.
• In the brain, the
hippocampus plays
a key role in spatial
memory and
navigation.
• https://www.youtub
e.com/watch?v=Kka
XNvzE4pk
Maguire (2000) Hippocampal
Volume
• The following examples illustrate how the
volume of the hippocampus can increase. Try
to explain why this might happen.
• 1. Animals that have a large territory
have larger hippocampi.
• 2. Small mammals and birds who
engage in lots of food storage have a
larger hippocampal volume.
• 3. Racing pigeons renowned for their
skill at flying home long distances from
unknown locations have larger
hippocampi than other breeds of
pigeon.
Maguire (2000) – Navigation
skills in Taxi Drivers
• Black Cab drivers are required to have a
detailed knowledge of the 25,000 streets
within a six-mile radius of Charing Cross as
well as a more general knowledge of the
major routes throughout the rest of London.
• They are given a written test on the first 80
routes and then interviewed on the other
240.
• http://www.taxiknowledge.co.uk/main.html
Have a look at a mock test and archives of
the top 50 routes requested.
Maguire (2000) – Navigation
skills in Taxi Drivers
• http://www.youtube.com/watch?v=wF8Uc
EHZjmg&eurl=http://www.psychexchange.
co.uk/videos/view/20196/&feature=player_
embedded clip of ‘The Knowledge’
showing London Cab drivers preparing for
the test.
• https://www.youtube.com/watch?v=hW6n
PfSqRRg
Maguire (2000) – Aim
• To investigate the role
of the hippocampus in
navigational and spatial
skills, and the extent to
which the brain shows
changes (plasticity)
when exposed to
extensive navigational
experience, as
demonstrated by
London taxi drivers.
• Also, to see if there
is a correlation
between the length
of taxi-driving
experience and the
measure of grey
matter volume.
Grey matter in the cerebral cortex
Maguire (2000) - Sample
• 16 licensed London taxi drivers.
• Right-handed.
• Aged between 32 and 62 (mean age of
44 years).
• Healthy medical, neurological and
psychiatric profiles.
Maguire (2000) – Sample
• A comparison group of 50 control
participants were chosen from the
structural MRI scan database at the
same unit where the taxi drivers were
scanned.
• All Male
• Non were taxi drivers.
• Right-handed
• Aged between 32 and 62. (Mean age
similar to taxi drivers)
Maguire (2000) – Method and
Design
• The method is best described as a QUASI
EXPERIMENT
• It also involves a correlational analysis.
• The IV is taxi drivers and non taxi drivers.
The DV is the volume of the hippocampus.
• The design is was INDEPENDENT
MEASURES
Maguire (2000) – Procedure
• With a partner discuss the procedure and
then evaluate its strengths and limitations.
• Once completed we will have a group
discussion
Maguire (2000) – Procedure
• Data was collected
using structural MRI
scans.
• The scans were
analysed using two
techniques:
• 1. VBM
(Voxel-Based
Morphometry)
• 2. Pixel counting.
Maguire (2000) – Procedure
• A structural MRI
(Magnetic
Resonance
Imaging) scan
involves using a
computer software
programme to
produce a 3D image
of the brain.
Maguire (2000) – Procedure
An MRI scan
• http://www.youtube.com/watch?v=PEDxW
LNZTA4
Maguire (2000) – Procedure
Analysing the MRI scans;
• 1st Technique – Voxel-Based
Morphometry.
Identifies differences in the density of
grey matter in different parts of the
brain.
Grey matter has dense neural
connections and is associated with
higher order thinking.
Maguire (2000) – Procedure
Analysing the MRI scans;
• – Pixel 2nd Technique Counting.
A pixel is a single point on a graphic image.
In order to calculate hippocampal volume, pixels
were counted on photographic ‘slices’ made
through the brain using an MRI scan.
The person counting the pixels was ‘blind’ to
whether the brain belonged to a taxi driver or
control participant.
Pixels were counted for the anterior, posterior and
body of the hippocampus.
Pixel Counting
Maguire (2000) – Procedure
• CONTROLS
• Participants were all scanned using
the same scanner.
• The hippocampal volume for each
participant was calculated to include
an adjustment for the size of each
person’s brain.
• This was to ensure that all participants
data was comparable.
Maguire (2000) – Procedure
• What about the results and conclusions?
• Again with your partner can you discuss
the results and conclusions and then
consider the overall strengths and
limitations of the study.
Maguire (2000) – Results
Maguire (2000) Results
• Volume – some regionally specific
differences were noted.
• Taxi drivers have greater grey matter
volume in their posterior right
hippocampus. (As measured by VBM)
• Controls have greater volume in their
anterior hippocampus.
• These results are significant at p <0.05
Maguire (2000) Results
Maguire (2000) Results
• Correlational Analysis – a comparison
of length of driving experience with the
measure of grey matter volume of the
taxi drivers showed a significant
positive correlation for the right
posterior hippocampus. r=0.6, p<0.05
• This means the more experienced the
driver is, the greater the grey matter
volume is in their right posterior
hippocampus.
Maguire (2000) - Conclusions
• Maguire states
‘professional
dependence on
navigational skills in
licensed London
taxi drivers is
associated with a
relative
redistribution of
grey matter in the
hippocampus’.
Maguire (2000) - Conclusions
• EXPLANATIONS FOR
RESULTS.
• 1. This difference in the
taxi drivers’ hippocampi
might have always been
there and this could have
led them to doing a job
where navigational skills
were important...... OR
• 2. The taxi drivers’
hippocampi may have
changed as a result of
studying for the
‘knowledge’ thus showing
plasticity of the brain.
Maguire (2000) - Conclusions
• The results of the correlational analysis would
support the second idea – because the longer
they had been a cab driver, the greater the
volume of their right posterior hippocampus.
Evaluation:
•
•
•
•
•
•
It is normally difficult to make conclusions form natural or quasi experiments
as any differences found between the two groups (e.g. volume of grey
matter) may not have occurred because of the independent variable (taxi
driver or non-taxi driver).
For example, it could be possible that people with certain brain differences
are attracted to certain jobs.
However, the researchers carried out a correlational analysis which clearly
demonstrated that there was a positive correlation between length of time
the participants had been driving taxi cabs and their posterior hippocampul
volume.
This suggests that length of time taxi driving is associated with grey matter
within the hippocampus.
The MRI scans provided the researchers with vast amounts of quantitative
data relating to the volume and size of the hippocampus enabling them to
carry out statistical analysis such as correlational analysis.
Although the task of being scanned in an MRI scanner is hardly ecologically
valid it would not be possible for the participants to respond to demand
characteristics.
• MRI scanning is of course a costly technique in terms of expensive
equipment and researchers? time, although the use of computers
does make very sophisticated analysis possible.
• MRI scanning technology does not pose any health risks to the
participants and all of the participants gave informed consent.
• None of the participants should have been negatively affected by
their experience.
• An obvious weakness of the sample is that the participants were all
male.
• There may be difference between males and females in terms of
spatial memory. We could apply the same argument to left handed
people
• The study employed many controls. For example the samples were
matched for age, sex and handedness. The pixel counting was
carried out by a researcher who was experienced in this technique
but blind to the participants condition.
Exam questions: