‘Turning a deaf ear’ blocks one ’s hearing

Turning a “deaf ear” to the outside world when preoccupied really does block the ability to hear, a study has found.

Scientists demonstrated that what they called “inattentional deafness” is a genuine phenomenon.

It is why a person can get “lost” in a page-turning novel or challenging crossword.

When this happens, the immersed individual becomes deaf to normally audible sounds.

Inattentional deafness occurs as a result of visual and hearing senses trying to share limited brain processing capacity, according to the research.

As well as being a source of irritation for those trying to be heard, it could be the cause of road accidents, experts believe.

Study leader 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 news-paper 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.”

A similar condition, “inattentional blindness”, has already been well documented, for instance by the famous “invisible gorilla test”.

In this experiment, observers become so engrossed in a basketball game that they fail to notice a man in a gorilla suit walking right across their field of vision.

Prof. Lavie’s team showed that sounds can also be blocked out when attention is focused in one direction.

More than 100 volunteers taking part in the study had to perform computer tasks involving a series of cross shapes.

Some tasks were easy, consisting of distinguishing a clear colour difference between the cross arms. Others were more challenging and involved identifying subtle length differences.

Volunteers wore headphones and were told these were to aid their concentration. At some point during a task 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 colours, only two in 10 volunteers missed the tone. But when focusing on the more difficult task of judging which of two cross arms was the longer, eight out of 10 failed to hear it. The findings were reported today 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,” said Prof. Lavie.

“In our task, most people noticed the sound if the task being performed was easy and did not demand their full concentration. But when the task was harder they experienced deafness to the very same sound.”

Inattentional deafness while driving is likely to be a contributing factor in accidents, said the scientists.

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 sat-nav map.