Karen's years of experience navigating the streets of a very large city as a taxi driver have resulted in changes in her brain's spatial memory centers that support her detailed street location memory. this best illustrates the value of

I believe the answer is: plasticity

Value of plasticity refers to the quality that obtained by a certain individual after performing a same task over and over again. This value is basically held by all living organisms, which buried deep in brain and most commonly recognized as survival instinct to adapt to the environment around us.