Here is a question for you: Given that the hippocampus is a brain structure that plays an important role in both memory and spatial navigation, who would you predict have a bigger hippocampus: A taxi or a bus driver?
You are right (see answer at the end of this post)!
In contrast to taxi drivers, bus drivers do not stimulate or challenge their hippocampus much, as they follow the same routes day after day. In a 2006 study researchers scanned the brains of London bus and taxi drivers and showed that on average taxi drivers had much bigger hippocampi than bus drivers.
This suggested that experience can shape the brain. You have probably heard that if you do not use your brain you may lose some of its functionality. Conversely, using and stimulating your brain may trigger the growth of brain cells and connections between them.
If you have a scientific and thus skeptical mind you may be wondering whether bus and taxi drivers’ brains are not different to start with anyway. People with a big hippocampus may be more attracted to and be more successful at being taxi drivers than bus drivers. In that case, the association observed between the size of the hippocampus and the type of job would not be a causal relationship and one could not conclude that experience shapes the brain.
To remedy this problem, the same researchers recently studied adults training to become licensed taxi drivers in London. The trainees’ brains structures and memory performance were compared to those of non-taxi driver controls. The study lasted 4 years, the time it takes for taxi drivers trainees to learn approximately 25,000 streets and their layout as well as 20,000 landmarks. At the end of the learning process all trainees took a series of exams that only about half passed.
To start with, taxi driver trainees and non-taxi driver controls showed no differences in either brain structure or memory. Three to four years later, the size of the posterior hippocampus had increased in the brains of trainees who qualified as taxi drivers. These changes were not observed in trainees who failed to qualify, or in the non-taxi driver controls.
This a great demonstration that the brain is shaped by our experiences. Such finding is an encouragement for all lifelong learners.
Woollett, K. & Maguire, E. A. (2011). Acquiring “the Knowledge” of London’s Layout Drives Structural Brain Changes. Current Biology, 08 December 2011
Answer: Taxi drivers!