Last year, Live Science published a nice little summary article (How the Brain Tunes Out Background Noise) about our mental process and how our perceptual process will tend to phase out the aspects of our surroundings which are routine or predictable:
The "novelty detector neurons," as researchers call them, quickly stop firing if a sound or sound pattern is repeated. They will briefly resume firing if some aspect of the sound changes. The neurons can detect changes in pitch, loudness or duration of a single sound and can also note shifts in the pattern of a complex series of sounds.
"It is probably a good thing to have this ability because it allows us to tune out background noises like the humming of a car's motor while we are driving or the regular tick-tock of a clock," said study team member Ellen Covey, a psychology professor at the University of Washington. "But at the same time, these neurons would instantly draw a person's attention if their car's motor suddenly made a strange noise or if their cell phone rang."
I'm interested in how this applies to driving-- there's a lot we need to attend to, as drivers, and a lot we don't even notice on a conscious level. How much of what we do when driving is necessary and how much of it is background? Do some people tend to have more trouble with the distractions than others? Do some of us have the ability to better distinguish background noise from necessary information?
As I am known to do from time to time, I will use birding as an example. When I'm looking for birds, I pay a lot of attention to the sounds and calls of birds, but I suspect that, after a short while, I do not pay any attention at all to familiar birds. Once I know that there are American Robins around, do my ears pay attention to them any longer, or do I just mentally dismiss them?
Or, on the other hand, we can think about music: when I am listening to a fairly common and unoriginal melody, I may not notice it at all on the surface, but I may notice unusual harmonies or arrangements of that same melody. Or, alternatively, unless I specifically attend to it, I may not even notice the chord progression of a tune, once it's gone through once or twice. Unless the music does something interesting, it may fade entirely into the background-- how often have you not even realized what song was playing on an intercom until someone pointed it out to you?