London taxi drivers aren't like the rest of us. Researchers have known for more than a decade that these elite cabbies—who train for years to master "the Knowledge," a mental map of 25,000 streets—have a larger than average rear hippocampus, a brain region linked to learning and navigation. What scientists didn't know was whether the drivers grew bigger hippocampi as they trained or whether they had big ones (and thus an innate navigation advantage) to begin with. So a team followed three groups—trainees who successfully acquired the Knowledge and became cabbies, trainees who failed to qualify, and a control group of non-taxi drivers—over 4 years, testing them and scanning their brains before, during, and after training. They found that the brains of qualifying trainees were no different from those of nonqualifying trainees or non-taxi drivers before beginning training. But as the cabbies learned the Knowledge, their hippocampi grew (see the progression from left to right), literally changing their minds, the researchers report online today in Current Biology. The hippocampi of unsuccessful trainees stayed the same throughout, which could suggest that successful cabbies really do have an innate advantage—their brains are more malleable than others'.
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