See more human senses pictures. Some of us are more adept at singing whilst gesturing than others. ©i Stockphoto.com /CREATISTA

A night out at the karaoke bar will likely confirm most of the suspicions you had about each of your co-workers. Yet, there may be one unanticipated surprise: In addition to not being able to hit the high notes in a Bette Midler song, the new guy in Accounts Receivable can't hit any notes at all.

As you watch him murder several songs over the course of the evening, another thing becomes quite clear: This guy -- grinning all the while and enthusiastically singing his heart out -- has absolutely no idea how bad he is.



Several things could be at play: the effects of a growing bar tab, a general indifference to singing, an immunity to embarrassment, or -- as is the case with about 5 percent of the U.S. population -- this person may be tone-deaf [source: Harvard Medical School].

If you suggest such a thing to another observer in the room, do so in a whisper. Tone deafness (also called amusia) has nothing whatsoever to do with actual deafness, so while your co-worker can't hear how bad he is, he can hear you talk about how bad he is.

The tone-deaf also have perfect hearing when it comes to music. However, what they perceive when they hear music is the sound of a perfect mess. Some tone-deaf people describe listening to music as something akin to listening to pots and pans clanging about. While the rest of us may wince when a tone-deaf person grabs the microphone, the tone deaf can't enjoy anyone else's singing at all. In that sense, karaoke night for the tone deaf is marked by a perfect reproduction of what music sounds like to them.

So what's going on?