Maguire (2000)

Uses: Neuroplasticity / Experimental Method (quasi-experiment) / Imaging technique (MRI)

Aim: to investigate how the brain structure of London taxi drivers is different from the average brain.

Method: Natural Experiment (Quasi)

  • Quasi experiments compare two pre-existing groups.

  • In maguire’s case it is a correlational study, where driving experience is corrleated with the grey matter volume.

Procedure:

  • MRI scans are completed between the experiment group and the controlled group. (All male, all taxi drivers have at least 1 year of experience after “the knowledge” test)

  • Correlated the number of years of taxi driving experience with the result of the scan.

  • Compared the scan between the experiment group and the controlled group.

  • Used VBM (voxel-based morphology) to measure the density of grey matter in the brain.

  • She also used pixel counting indicates the volume or size.

  • Maguire did not tell researchers which MRI is the taxi driver or the control subject's MRI which neglects bias. (Single Blind)

Results:

Using pixel counting, taxi drivers had increased amount of grey matter in their posterior hippocampus while the controlled group have greater anterior hippocampus volume. The VBM showed that the density of the right posterior hippocampi correlated with the amount of time spent as a taxi driver. Which means the longer the taxi driver drove the taxi, the denser their right posterior hippocampus, vice versa. This means grey matter are redistributed from the anterior to the posterior the longer the taxi driver drove the taxi.

Conclusion:

Redistribution of grey matter in the hippocampus occurs in taxi drivers in response to gaining navigational experience.

Background knowledge:

Posterior hippocampus is known to be involved in utilizing previously learned spatial information, therefore the taxi drivers need this information to know the streets of London. On the other hand, anterior hippocampus is known to be responsible for learning new spatial information. Hence, the longer they drove the taxi, the less new spatial information they need to learn. This resulted in smaller anterior hippocampus volume.

Evaluation:

Pros:

  • The experiment is conducted in a non intrusive way following the ethical guideline. The results seemed to be aligned with the theory.

  • Controlled, single blind, shared experiences.

Cons:

  • Correlational.

  • Niche sample.

  • Shows structural change, can not be directly observed.

Maguire, E.A., Gadian, D.G., Johnsrude, I.S., Good, C.D., Ashburner, J., Frackowiak, R.S., & Frith, C.D. (2000). Navigation-related structural change in the hippocampi of taxi drivers. Proceedings of the National Academy of Sciences of the United States of America, 97 8, 4398-403 .