Many of us have probably been accused of not paying attention to what someone is saying to us. I’ve also found it odd (since I can’t recall it happening to me) when I’ve approached someone engaged in a task, and they genuinely seemed not to notice I was there.

In a study published in Attention, Perception, & Psychophysics, a group of researchers have been examining a condition called “Inattentional deafness.” The group from University College London examined study participants’ ability to detect a sound while focusing intently on a task.

When subjects did a simple version of the computer based task, most recalled hearing a soft tone (that they were not expecting) in their headphones. A very difficult task caused most participants to become totally unaware of that same stimulus.

Although the study may fuel excuses the next time you are accused of not listening, it has more serious implications as well. While a frenetic pace of life puts a premium on people who can “multitask,” this study emphasizes that multitasking is not something the brain has limitless capacity for. Texting, having conversations, or just daydreaming while we are driving, are all instances of things that rob us of our ability to focus. Having any kind of inattentional deafness or blindness may does not necessarily have to cause the level of impairment that alcohol may bring, but may still cost precious seconds of reaction time that could mean the difference between avoiding an accident, or causing one.