The big advance here is that the current study shows that the brain change occurred directly as a result of the learning. Previous studies had a weakness in th

The big advance here is that the current study shows that the brain change occurred directly as a result of the learning. Previous studies had a weakness in that they only looked at brain size well after the learning had occurred; raising the possibility that people with bigger hippocampi choose to become taxi drivers, or are the only people who pass the test. So the new study established causation, extending our knowledge beyond the correlation.