“The Knowledge” of a London Taxi Driver

by Edward Quinn

​Our readings this week focus on the embodied effects of training in specific subcultural contexts. A very interesting example of this phenomenon can be found among taxi drivers in London. Becoming a taxi driver in London is an arduous, 3-4 year process that is cognitively demanding. Taxi drivers must learn the spatial characteristics of an area within 6 miles of Charing Cross train station, which contains roughly 25,000 streets. Only about half of the people who set out to become a taxi driver in London typically complete the training and exams required for qualification.
 
The hippocampus is an area of the brain that is associated with memory formation and spatial navigation, so it is reasonable to infer that the hippocampus is a particularly important brain structure for a London taxi driver. Woollett and Maguire (2011) build on previous cross-sectional studies showing greater gray matter volume in the posterior hippocampi of taxi drivers compared to matched controls who were not taxi drivers. Using a longitudinal research design with two time points, the authors tested the hypothesis that what drives these observed differences in the hippocampus is the 3-4 year taxi driver training process of acquiring “The Knowledge” of London’s spatial characteristics. They started off with two groups at Time 1 (taxi driver trainees and matched controls) and ended with three groups at Time 2 (qualified taxi drivers, failed taxi trainees, and controls).
 
The authors found confirmatory evidence for their hypothesis. Qualified taxi drivers showed increased gray matter volume in the posterior hippocampus compared to matched controls and the group of failed taxi trainees at Time 2. The longitudinal research design lends particular strength to these findings, and gives us a reasonable basis for inferring cause and effect. In addition, the authors show that qualified taxi drivers actually performed worse than the control group on a memory recall test of a complex figure at Time 2, but not at Time 1.
 
This last point is interesting because it suggests that there may be a cost to cognitive specialization driven by culturally specific training regimens. The training regimes people subject themselves to enable adaptation to particular demands, and this is a good thing so long as the demands do not change. It may be the case that the structural changes associated with qualification as a taxi driver actually inhibited performance on a short term (30 minute) memory test. If this is the case, it would be interesting to further explore not only the strengths people are able to develop through intense training, but also what weaknesses come as a cost of that same training.
 
From a neuroanthropological perspective, we might have predicted that the training regime of London taxi drivers might be embodied in the form of structural changes in the brain. While MRIs provide a method of testing this idea, it might be enhanced by doing the ethnography of a London taxi driver. It would be interesting to hear how a London taxi driver describes the training process, and ethnography may corroborate the findings of Woollett and Maguire (2011). Also, neuroanthropologists place great emphasis on the importance of environmental input for the developing brain, with less emphasis on adult plasticity. This study used groups of men with average ages of 35, 38, and 41, thus providing an example of plasticity in the brain long after development is complete. It is important to remember that enculturation of the nervous system does not end with development, as clearly demonstrated by the taxi drivers of London.  
 
Overall, this is a great article with interesting implications for neuroanthropology. The idea that training regimes come with not only adaptive benefits, but also costs is an idea that deserves to be further explored. In neuroanthropology, plasticity in adulthood seems to receive less attention than plasticity in developmental stages of the life course, but this study shows that plasticity can be important in adulthood as well. The longitudinal research design lends great strength to the evidence for the embodied effects of training to be a taxi driver in London, and neuroanthropologists might benefit greatly from implementation of strong research designs such as the one used by Woollett and Maguire (2011).
 
Reference:
 
Woollett, Katherine, and Eleanor A. Maguire. 2011. "Acquiring ‘the Knowledge’ of London's layout drives structural brain changes." Current Biology 21(24): 2109-2114.