About this passageSummarised for this collection from the London taxi driver studies, which are the most cited demonstration that an adult brain changes structurally with sustained practice. The 2011 study is the one that matters most, because it followed trainees over time rather than comparing drivers with non-drivers — which is what rules out the possibility that people with larger hippocampi simply become taxi drivers.
London taxi drivers spend three or four years learning the city's layout well enough to pass an examination called the Knowledge. When researchers scanned them, the rear part of the hippocampus — a structure involved in spatial memory — was measurably larger than in people who had not done it.
That first result had an obvious weakness: perhaps people with that kind of brain are drawn to that kind of job. So a later study followed trainees from before they started. Those who qualified showed the structural change. Those who trained and did not qualify, and those who never trained, did not. The change followed the practice.
Two things worth keeping in proportion. This was years of daily effort, not a technique applied for a fortnight, and the change was specific to what was practised rather than a general improvement — on some other memory tasks the qualified drivers did slightly worse.
What the finding supports is narrow and still considerable: an adult brain is not finished. What you do repeatedly, over a long time, shows up in the tissue.