1. Maguire et al. (2000) (AS) Navigation-related structural changes in the hippocampus of taxi drivers

2. Background This study focuses on the role of the hippocampus.
This is a part of the brain located in the temporal lobe in the limbic system.
Humans have two hippocampi: one on each side of the brain.

3. What is grey matter?
Grey matter is tissue in the nervous system that appears grey because it is composed of numerous nerve cells and blood vessels.
White matter is creamy white in its appearance due to the fatty myelinated sheath on the neurones.

4. Animal research
One role of the hippocampus is to aid spatial memory in the form of navigation.
Animals and birds that migrate and store food have an increased hippocampal volume relative to brain and body size.
This is the function of the hippocampus that this study investigates.

5. General aims
Could the structure of a person’s brain be altered as a consequence of the demands they make on it? (This is known as plasticity.)
For this to be tested, Maguire needed a group of people who used one part of their brain (the hippocampus) extensively. London taxi drivers are required to learn a lot of spatial information (roads, landmarks, etc.) and so Maguire used taxi drivers as part of her sample.

6. Spatial memory and navigation
The hippocampus is important in navigation.
The size of the hippocampus is enlarged in animals that rely on navigation, e.g. squirrels and birds that store food in multiple areas.
The idea that our memory is linked to how well we navigate arises from the concept of cognitive mapping.
Cognitive mapping is the idea that we all have mental representations of the world around us, and use these mental representations to guide us to know where to go and to remember where we have been.

7. Cognitive maps
We all represent the world around us in different ways and some of us will be naturally better at navigation than others.
Can you think of any examples of people who are good at navigating and/or spatial memory tasks?
What we want to find out is if navigation ability is linked to the size of our hippocampus.

8. Method of research
How could we measure the changes in a human’s hippocampus?
One way of investigating these differences is to use a brain imaging technique known as an MRI (magnetic resonance imaging).

9. MRI
Magnetic resonance imaging is a scanning technique using a strong magnetic field and radio pulses.
Patients lie in a round tunnel, surrounded by a large magnet, which generates a powerful magnetic field.
Part of the body is ‘magnetised’ and exposed to radio pulses that cause the tissues to give off radio signals that can be measured.
This allows a picture to be built up of the part of the body that the research is interested in.

10. Aims
To investigate the differences in the hippocampi of London taxi drivers compared to controls.
Also, to further investigate functions of the hippocampus in spatial memory.

11. Participants 16 male London taxi drivers
All right handed – Why not use left-handed people?
Between ages 32 and 62
Been licensed for at least 18 months (range: 18 months to 42 years)
All passed ‘The Knowledge’
All healthy medically, neurologically and psychologically – Why is this important?

12. Control group
Participants were needed to compare to the taxi drivers (the experimental group).
Researchers selected 50 scans from the MRI database at the centre where the taxi drivers were scanned.
All were healthy right-handed males aged between 32 and 62.
None of the control scans was from taxi drivers.

13. Research method What research method does Maguire use?
Does the study have a dependent variable? Is it controlled?
Does the study have an independent variable? Does the researcher manipulate this?
The study is a quasi experiment as the IV is naturally occurring.

14. Method
Data was collected through two techniques used to analyse MRI scans – Voxel-based morphometry (VBM) and pixel counting.
Data was also correlated with the length of time the taxi drivers had been licensed.

15. Pixel counting
This was carried out by one experienced person. It is a 2D measure of area. The scans were separated into ‘slices’ from the posterior/anterior and main body of the hippocampus – so differences in these areas could be detected.
The name hippocampus is derived from the Greek word for seahorse (hippos = horse, kampos = sea monster).

16. Voxel-based morphometry (VBM)
This is an objective 3D measure of the volume of grey matter in the brain (calculated from the MRI scan by computer).

17. Results
Significantly increased grey matter volume was found in the taxi drivers’ brains compared to the controls’ brains in the posterior (back section) hippocampus.

18. Correlation results
Length of time spent as a taxi driver correlated positively with volume in the posterior hippocampus.

19. Correlation results
Length of time spent as a taxi driver correlated negatively with volume in the anterior hippocampus.

20. Conclusions
The study showed regional differences between the hippocampi of London taxi drivers compared to a control group of non-taxi drivers.
It seems that professional dependence on navigational skills is associated with a redistribution of grey matter in the hippocampus.

21. Cause and effect
Was I destined to be a taxi driver due to my hippocampal grey matter distribution?
*not a quote from the film*
Is it possible that having this particular arrangement of hippocampal grey matter could predispose individuals to jobs such as taxi driving?

22. Cause and effect
It seems not. Instead, my hippocampus seems to have increased in volume due to the demands of my job. Interesting…
The correlational data indicates that hippocampal volume increases with the amount of time spent as a taxi driver.
So increased exposure to an environmental stimulus (i.e. navigational skills) can lead to changes in the brain’s plasticity.
Maguire – One Show

23. Evaluation Validity Ecological validity Reliability Ethics Other
Is the study controlled?
How does using two different measures (VBM and pixel counting) affect validity?
Ecological validity
Is being scanned an everyday task?
Is there any way the results are not a true reflection of the participants’ brain structure? Could they be affected by demand characteristics?
Reliability
Does the use of scientific equipment increase or decrease reliability?
How does the sample size affect reliability?
Ethics
Are there any ethical concerns in this study?
Other
Psychology aims to be considered a science. Is this study scientific?
Where does this study sit in the nature/nurture debate?

24. Links to debates
Would you categorise this study as scientific? Justify your opinion.
Studies that come under the biological area are often associated with the nature side of the debate. Is this true of Maguire’s study? What is it that caused the change in the hippocampus volume?

25. Links to areas/perspectives
Maguire’s study falls within the biological area as it studies the plasticity of the human brain.
The measures (dependent variables) in this study specifically look at the biology of the participants (volume and area of grey matter in the hippocampus).

26. Links to key themes
The key theme of this study is brain plasticity. Maguire investigates this by looking at the difference between taxi drivers and non-taxi drivers in terms of hippocampus volume.
The study clearly shows that if you use a specific area of the brain (in this case the hippocampus) a lot then your brain is able to adapt to this increase in demands.
This study furthers our understanding of the key theme by suggesting that brain plasticity is a phenomenon found not only in cats (Blakemore & Cooper), but in humans as well.
Individual, social and cultural diversity – Due to the differing samples this study is hard to compare with Blakemore and Cooper in terms of diversity. However, the contemporary study (Maguire) does show how similar techniques as used with animals can be used on humans. The study also shows how individuals differ in terms of their memory. In this case memory depends on the environmental demands placed on it.

27. Blakemore and Cooper vs. Maguire
Use your comparison sheet to compare the two studies. Below are some questions that may help you.
Sample size?
In what way is the measurement of the DV similar between the two studies?
Do the lengths of the studies differ or are they the same?
What do they both conclude?
Data type?