You're sitting at the breakfast table, checking your email or reading last night's sports scores, and your spouse asks you a question -- and you don't respond. Then comes the inevitable: "Are you listening to me?" And you nod your head but really haven't heard a thing.

If this scenario sounds familiar, science has just provided you with the perfect excuse -- and it's not "selective hearing." Thanks to research recently published online in the journal Attention, Perception, & Psychophysics, you can blame it on "inattentional deafness."

A newly-identified phenomenon that's common in everyday life, inattentional deafness occurs when your attention and focus are placed on a visual task, so you tune out the sounds around you. For example, you may be immersed in the latest must-read bestseller and miss the announcement for your bus or train stop. You could be fiddling with a new cell phone app while crossing the street and not hear an approaching car. You could be driving down the street and glancing at a hot chick in a skimpy outfit but fail to notice the beeping of a truck backing out of a driveway.

When your mind is busy elsewhere, it seems to turn down the volume on other noises around you. "Inattentional deafness is not about where your eyes are, it's where your mind's eye is," says Nilli Lavie, a professor of psychology and brain sciences at the Institute of Cognitive Neuroscience at University College London.

In the study, Lavie and a colleague conducted a series of experiments on more than 100 volunteers who had perfectly normal hearing and vision. Participants were asked to wear headphones during the test to supposedly help them concentrate. In truth, though, the headphones sometimes unexpectedly produced an audible tone. 

Volunteers first did an easy task -- noticing the colors of two crossed lines on a computer screen. When asked, eight out of 10 remembered hearing the tone during this simple test.

But during a harder task that required more concentration -- identifying the larger of two crossed lines -- the results were reversed: Eight out of 10 missed hearing the same exact tone.

The findings suggest that "your perception of sounds depends not just on your sense of hearing but also on your ability to pay attention," explains Lavie, the study's lead author. "It's the first time that we've shown that people are not able to detect an ordinary tone if they're engaged in a task that demands full attention."

Hearing is thought to have developed as an early warning system that does not hinge on attention. So the British scientists were surprised to discover attention mattered: In this research, hearing abilities changed because of mental processing.

Inattentional deafness is the hearing equivalent of "inattentional blindness," a failure to see unexpected things when your brain is concentrating on something else. Body Odd has previously written about the Invisible Gorilla experiment, where people who were busy counting basketball passes often missed seeing the obvious -- a man in a gorilla suit crossing the court. 

And while they haven't looked at the mechanism that makes you deaf to the world around you, it likely works along similar lines to the ones that blind you. Lavie suspects the part of the brain responsible for interpreting sound is registering a weaker signal because it's involved in another task that's taking up all its attention.

Do you have any funny stories from your own "inattentional deafness"? Pray tell.

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