The body of studies that led to the understanding of neuroplasticity involved different groups of individuals, like taxi drivers in London, whose posterior hippocampi had larger volumes compared to people whose work did not depend as heavily on spatial navigation skills. When these studies were done, taxi drivers in London needed to undergo extensive training, learning how to navigate between thousands of roads in the city. Back then, before the GPS, it was necessary to pass a very stringent test which measured knowledge of how to navigate the city from memory, in order to become licensed. Therefore, London taxi drivers were ideally suited for the study of spatial navigation, a function that in large part depends upon the hippocampus. Studying this group would allow researchers to understand whether brain differences were the result of experience or the result of pre-existing differences among people. Researchers discovered that hippocampal volume increased in these drivers as a function of the amount of time spent as a taxi driver. This answered the question. Driving a taxi in London shaped the structure and function of the brain in a way that was different from non-taxi drivers.
Similar results have been shown for other groups like professional stringed instrument players, who had increased brain volume compared to non-musicians and amateurs, and braille readers who showed unique brain changes in the somatosensory cortices.
These lines of research paved the way for understanding the effects of practice on the brain.