We can all recall times when we were so engrossed in something that we were oblivious to our surroundings.
Regularly recurring sounds also often don’t register, especially if they don’t require any reaction from us. An example is people living next to a railway line who don’t hear the passing trains anymore.
There’s a difference between physically hearing a sound and consciously registering it. To put it simply, you “hear” what you focus on or pay attention to – even if you choose not to react. A case in point is when someone at a cocktail party manages to drown out the peripheral noise to have a conversation with one or two people.
Selective hearing is not necessarily a case of people pretending not to hear, it’s actually a way for our brains to filter out extraneous noise so we can concentrate on what’s important at that moment.
A scientific explanation
In fact, a 2012 article in the journal Nature, explains how two scientists from the University of California, San Francisco solved the mystery of how selective hearing works in the brain, i.e. how people can tune into a single speaker while tuning out a noisy environment.
Test subjects listened to two speech samples simultaneously but were led to focus on only one speaker. The authors then “reconstructed” what the subjects heard and found that neural responses in the auditory cortex reflected only the words of the speakers that the subjects focused on.
Their decoding algorithm could predict which speaker and even what specific words the subject was listening to, based on their neural patterns.
This shows that the brain is indeed capable of homing in on targeted sounds while tuning out the rest.
Who’s more selective, men or women?
Selective hearing is associated more with men than with women. Men might appear to ignore their female partner until she mentions something that is of interest to him like the latest cricket score, and then reply as if he had been listening all along. This kind of interaction, or lack of it, is actually very common among people of both sexes and all ages.
The theory is that not too long ago when we were hunter-gatherers men survived by being able to concentrate totally on one thing at a time, for example in a hunting situation. Women, on the other hand, thrived by being aware of more than one thing at a time, like listening to what the children were up to while gathering fruits and nuts.
How do we hear?
Basically, sound waves enter our ear canals, where our inner ears translate them into nerve signals – and once these signals are processed by the auditory cortex in the brain we become conscious of the waves as sounds.
Before the sound waves reach the inner ear, they encounter the external parts of the ear that stick out on both sides of the head. These bits are called pinnae or auriculae, and work like funnels that collect, amplify and direct the sound waves to the ear canal.
The human pinna is designed to enhance sounds with a pitch that is typical of a human voice. These sounds are enhanced up to 100 times, largely ignoring other pitches, which certainly helps the auditory cortex to tune out unwanted or irrelevant sounds. The pinnae also help us deduce where sounds are coming from.
To illustrate how well designed the outer ear works is the issue of hearing aids and background noise. Even the best hearing aids are not as effective as the human ear and don’t have the ability to distinguish between background noise and what the person is trying to focus on. This means that people who wear hearing aids are bombarded with the full spectrum of noise, turning social occasions into a bewildering cacophony of sound.
Causes of hearing loss
There are many factors that can lead to partial or complete hearing loss. Causes of deafness can be pre- or post-natal, meaning before or after birth. Deafness can also be temporary (as in the case of a removable blocking agent) or permanent.
According to the World Health Organisation:
- Worldwide 360 million people suffer from disabling hearing loss.
- The cause of hearing loss may be genetic, complications at birth, infectious diseases, chronic ear infections, the use of particular drugs, exposure to excessive noise and ageing.
- Half of all cases of hearing loss are avoidable by means of primary prevention.
- People with hearing loss can be assisted with hearing aids, cochlear implants and other assistive devices; captioning and sign language; and other forms of educational and social support.
- Current production of hearing aids covers less than 10 percent of global requirements.
WiseGeek: What is Selective Hearing? http://www.wisegeek.org/what-is-selective-hearing.htm
Scientific American: Ears: Do Their Design, Size and Shape Matter? http://www.scientificamerican.com/article/ears-do-their-design-size-and-shape-matter/
Healthy Hearing:Hearing Aids and Background Noise: Overcoming the Battle. http://www.healthyhearing.com/content/articles/Hearing-aids/Awards/41066-Hearing-aids-background-noise