Final answer:
The hippocampal formation can enlarge in response to prolonged and demanding cognitive tasks, such as spatial navigation involved in driving a taxi in a complex city like London.
Step-by-step explanation:
An enlarged hippocampal formation would be expected in option a. a London cab driver who has 30 years of experience.
Multiple studies have shown that the hippocampus, a structure in the brain related to learning and memory, undergoes structural changes in response to environmental factors, including spatial navigation and extensive learning experiences.
For example, a study conducted on London cab drivers found that those with more years of experience and extensive training had larger hippocampal volumes compared to non-taxi drivers.
These findings suggest that the hippocampal formation can enlarge in response to prolonged and demanding cognitive tasks, such as spatial navigation involved in driving a taxi in a complex city like London.