Turning down the radio instead of looking at a map when you find yourself lost or driving on unfamiliar roads may seem like a strange thing to do, but as it turns out, it's not strange at all. It's your brain's natural reaction to the circumstances.
In order to understand why you turn down the radio when you're lost, you have to understand a few things about how the human brain works. The human brain has three parts: the cerebrum, the largest part of the brain, and the part that controls your higher cognitive functions such as language and emotions; the cerebellum, which controls your muscle movements and balance; and the brainstem, which controls all the body's automatic functions, such as breathing, as well as acting as the relay station between the spinal cord and the cerebrum and cerebellum.
As you go through your day, you collect information about your environment through your five primary sensory systems: taste, hearing, smell, touch and vision. Each sensory system has its own sensory neurons, and each tells the central nervous system about changes in your environment. The brain, which is part of the central nervous system, combines all this information and decides how to proceed. That process is called encoding. The brain is constantly evaluating what should be its primary task — the chief task the brain focuses on — and its secondary task, the concurrent task that gets less focus.
The brain's ability to switch back and forth between its tasks is called attention switching, and it comes with a price: When the brain switches its focus and attention from one task to another it's fast, but it's not instantaneous. Those fractions of a second spent attention toggling may slow down your performance, including minor delays in your reaction times. And when you're lost, that could mean the difference between seeing or not seeing the street sign you need to spot.
People often turn down the radio when driving in crowded urban areas, looking for a specific address, or driving in dangerous conditions (such as torrential rain or during a snowstorm) because those activities require more concentration than during a typical drive. Turning the radio down or off eliminates a task from the brain's to-do list, shifting its focus to the most important task: finding the way.