Becoming engrossed in a good book or a crossword really can block the ability to hear, a study has found.
Scientists demonstrated that when someone focuses their full attention on something, they can become deaf to normally audible sounds. It happens because visual and hearing senses are trying to share limited brain capacity, they said.
But it can have serious consequences, and could be the cause of some road accidents. The phenomenon is known as "inattentional deafness".
study leader Professor Nilli Lavie, from the Institute of Cognitive Neuroscience at University College London, said: " 'Inattentional deafness' is a common everyday experience. For example, when engrossed in a good book or even a captivating newspaper article, we may fail to hear the train driver's announcement and miss our stop. Or if we're texting while walking, we may fail to hear a car approaching and attempt to cross the road without looking."
In the study, 100 volunteers performed computer tasks involving a series of croSome were easy, such as being able to tell that the arms of the cross were different colors. Others were more challenging and involved identifying subtle length differences.
At certain points, a tone was played unexpectedly through the headphones, after which the experiment was stopped.
Participants were then asked if they had heard the sound.
When judging colors, only two in ten volunteers missed the tone. But when focusing on the more difficult tasks, eight in ten failed to hear it.
Prof Lavie wrote in the journal Attention, Perception And Psychophysics: "Hearing is often thought to have evolved as an early warning system that does not depend on attention, yet our work shows that if our attention is taken elsewhere, we can be effectively deaf to the world around us."
It is well known that many road accidents are caused by drivers' inattention.
Sounds such as a lorry beeping while reversing, a cyclist's bell or a scooter horn could all be missed by a motorist focusing intently on visual information from a road sign or satellite -navigation map.