This has actually been researched.
The thought of using a paper map instead of your smartphone or an in-dash GPS navigation system may seem absurd to people today, especially for those under the age of 30. But there was a time, not so long ago, when we relied on good old paper maps and street signs. According to MIT Technology Review, utilizing those older methods may have been better for our brains while opting for GPS could be making us dumber. A series of experiments at University College London were recently conducted to investigate this further.
Volunteers were tasked with navigating simulations of the Soho area of London. Scientists had fMRI scans capture their subjects' brain activity during those simulations, which sometimes had them find their own routes, or were given turn-by-turn directions like those in a car's GPS or on the Waze smartphone application. And guess what? The results showed "spikes of neuronal activity in (the) hippocampus, a brain region linked to navigations, and the prefrontal cortex, associated with planning," occurred as the subjects entered new streets. However, those spikes were more pronounced "when there are more possible choices to make on an upcoming stretch of road." That activity wasn't observed when people received turn-by-turn directions.
"When we have technology telling us which way to go...these parts of the brain simply don't respond to the street network," explained the lead researcher to The Guardian. "In that sense our brain has switched off its interest in the streets around us." But is that actually making us dumber? Kind of, yes. "If you think about the brain as a muscle, then certain activities, like learning maps of London's streets, are like body building...you're not working out these particular of the brain when you're relying on (turn-by-turn directions)," the same researcher explained to Scientific American. Humans found their way with paper maps for a long time before GPS arrived; the method is long proven.