Act of focusing shuts out noisy world

New research by the University College London suggests that focusing heavily on a task actually shuts out perfectly audible sounds.

"Inattentional deafness is a common everyday experience," explains Nilli Lavie from the Institute of Cognitive Neuroscience at the University College, according to a report in the journal Attention, Perception and Psychophysics.

"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 whilst walking, we may fail to hear a car approaching and attempt to cross the road without looking."

Lavie and her doctoral student James Macdonald devised a series of experiments designed to test for inattentional deafness, the report said.

In these experiments, over 100 participants performed tasks on a computer involving a series of cross shapes. Some tasks were easy, asking the participants to distinguish a clear colour difference between the cross arms.

Others were much more difficult, involving distinguishing subtle length differences between the cross arms.

Participants wore headphones whilst carrying out the tasks and were told these were to aid their concentration. At some point during the task a tone was played unexpectedly through the headphones.

At this point the experiment was stopped and the participants were asked if they had heard this sound.

When judging the respective colours of the arms - an easy task - around two in 10 participants missed the tone.

However, when focusing on the more difficult task - identifying which of the two arms was the longest - eight out of 10 participants failed to notice the tone.

The new research shows that being engrossed in a difficult task makes us blind and deaf to other sources of information.