Auditory Processing and the Brain


Steven Michaëlis

Most learning and development takes place by taking in information through the sense of hearing using our ears, through the sense of vision using our eyes and through touch and movement. Of all the senses these three, more than any of the other senses, determine how well we develop from a new born baby to a well adjusted adult that can successfully function in life.

Hearing involves more than just our two ears, as these are only the receptors that gather sound from the outside world. How this information is processed and interpreted in the brain will to a great extend determine how we perceive reality and how we react, behave and express ourselves. The ears and the associated processing centres in the brain form our auditory system.

Listening to the voices around us, that of our mother, father or siblings for instance, is how we acquire understanding of language, and learn to speak. Extensive periods of reduced hearing during the first years of life, though ear infections or medical conditions, will often impact on language and speech development. Imperfections in how we hear or process sounds will often show themselves in how we speak or how well we can read and write.

Sounds received through our right ear is mainly processed in the left brain half and sounds coming into our left ear are mainly processed in the right half. The brain uses these two separate and slightly different signals to calculate location and movement of sounds. The two sides must work well together in order to be able to filter out distracting sounds that come from other sources, for instance, the sound of the mother's or teacher's voice. People with attention deficit are often distracted by unrelated sounds in their environment. Faster transfer of information between the two brain halves, through the Corpus Callosum – the main bundle of connecting fibres between the two brain halves – is of essence.

Reading and writing are complex processes involving not only visual abilities, but also relying on effective auditory processing. The process of reading and writing involves us speaking to ourselves, quietly inside our head and then listening to our ‘brain voice’. Only then are we able to understand what we are reading or writing. Brain scans clearly show that the same hearing processes are activated when we are listening to ourselves in our head during reading or writing as when we are listening to an external voice using our ears. And likewise, we use the same specialised speech production centres in the brain when talking to ourselves in our own brain, as when we are speaking aloud to someone. Poor auditory processing will lead to slow or inaccurate reading and writing. Many people diagnosed with Dyslexia have difficulties in accurately processing fast or very short sounds.

You know if you are right or left handed, unless you belong to the very select group of naturally ambidextrous people who are equally at ease using their right hand or their left hand for all tasks. There is also mixed handedness, where some tasks are more easily performed with one hand and other tasks more easily with the other hand. But apart from these exceptions to the rule, most people are either right or left handed. You may also know which leg you prefer, for instance when kicking a ball or when starting to go up or down stairs.

But do you know which ear you prefer? Like right or left handedness, most people are either right or left eared. This matters as there is a speech specialisation in the brain, with the majority of people processing language understanding and speech production in the left brain half. As the right ear is directly connected to the left side, this is the most effective ear to understand language and express ourselves through speech.

If we listen to speech mainly through our left ear, then that information will first be received by the right side of the brain. But the right side does not understand language, so the signal needs to be re-routed to the other side, to the left brain-half where our language centres are located. This will take a little time, and that delay may make it more difficult to decipher short sounds or to accurately understand speech.

When we are talking we listen to our own voice to give us feedback of how we are speaking. Try talking with your ears well covered. You will not know how loud you are speaking, and most people will also slow down as speaking becomes more difficult. People that mainly use their left ear to listen to their own voice will experience a short delay before they can process the speech, and in some that may lead to more hesitant speech or even a stammer.

We now know that it is not so easy to change hand dominance from the left to the right. For over one hundred years many left handed children were forced by teachers to use their right hand for writing. Although many learned to write really well with their right hand, it did not really shift their hand preference. Most professional footballers train their ‘other’ foot to become better, as that gives them more options and skills, but they remain either right or left footed. As far as ear dominance is concerned it is fortunately easier to induce a shift from the left to the right.

Speeding up the brain

There is little doubt that faster and more efficient processing in the brain will help a person to perform better and achieve more. But is it possible to change how the brain processes information? It is not something that we think about every day and may seem more science fiction than reality. But throughout life we are interacting with our brain to do exactly that. The first time we had a typewriter or computer keyboard in front of us, we were dazzled by all those buttons, with the letters scrambled up in a totally illogical follow-order. But then, for most of us at least, we slowly started to learn which letter is where and how to control the typewriter or computer. We learn to use the keyboard faster and more automatically. This is directed by our brain which now can remember better and operate our fingers faster. We have made a long lasting change in the function of our brain.

We know that when we repeat a particular exercise again and again, that the brain will become increasingly better at processing that particular set of instructions. We may exercise a golf swing, new words in a foreign language or mathematical equations. Repeated exercise will improve our performance and achievement. Not only do we get better by doing these repeated exercises, but the new skills will also stay with us for some time. They get imprinted in our brain. Once we’ve learned to ride a bicycle, for instance, the skill will stay with us for a lifetime. We may get a bit rusty after a long time of not cycling, but it will come back to us very rapidly once we get on a bike again. The memory of the various bike riding skills are still stored in our brain.

A very effective way to train the brain to speed up processing and make faster connections between the two brain-halves is by using sound through headphones. As described earlier, sounds that come in through our right ear are mainly processed in the left side of the brain, while sounds from the left ear go to our right side. Through the use of headphones that totally cover the ear, so called full-sized headphones, and by using specifically recorded and processed music, we can now control which side of the brain is activated.

When we direct a sound only to the right ear, we will hear the sound coming from the right and process it with the left side of the brain. Then if we move this sound to the other side by increasing the volume in the left ear and reducing the volume in the right ear, we will move the processing from the left to the right side of the brain. At some point, when the sound is equally loud in both ears, the sound seems to be coming from the front and at this point the processing will be transferred from one brain half to the other. Interestingly, we perceive this transfer of processing as a totally smooth transition. If there was no coordination between the two sides of the brain, we would be very surprised to suddenly hear a sound appearing on the left side, processed by our right brain half. Fortunately the brain sends a signal to the other side, though the Corpus Callosum, to prepare it for the impending processing task. To us the sound moves effortlessly from the right to the left, without hick-up or surprise when it goes through the middle.

By moving sound from one side to the other we can instruct the brain to send signals in the opposite direction between the two brain halves, through that main connecting cable, the Corpus Callosum. Now, the brain is clever, and it will rapidly detect patterns in any incoming signal. Most music consists of a constantly repeating theme, rhythm or beat, with only a small variation woven into the tune. The brain rapidly detects the repeating pattern and will start to anticipate what comes next. This is great when we’re listening to music for entertainment, but it will reduce the brain’s attention to the sounds and put the brain into auto-pilot mode. To achieve an effective intervention and to ensure the brain stays fully attentive and active, it is better to minimise the predictability of the music, while still retaining the concept of music. By building unexpected events into the music the brain will be fully activated. It will know it is listening to music, it will expect a very regular pattern, but it will constantly be surprised by the random variations. The brain will therefore need to stay on it’s toes in order to cope with this unusual input. This constitutes an auditory work-out for the brain, something we rarely provide to our brain. It will strengthen and speed up the processing.

Exercising the auditory processing centres in the brain in this way will make for faster connections, which in turn can help with attention, concentration and understanding. With many clients we have also noticed improvements in organisational and time management skills, while impulsiveness is often reduced. Faster processing and better connections between the two sides of the brain will help, but there is more that we can do, using the same technique with sound through headphones, so read on.

Synchronising the two sides of the brain

It is the left side of our brain that ensures that we understand language and produce speech, but it is the right side of our brain that looks after the intonation of our speech. This was discovered around 150 years ago, when doctors noticed that patients with a stroke on the left side of the brain often lost speech, and that those with a stroke on the right side mostly spoke in a monotonous voice, without any intonation, rhythm or stress.

Just to reiterate, sounds picked up by the right ear are processed in the left brain-half and vice versa, then how is it that we perceive an uninterrupted and smooth movement of sound when, for instance, standing on the side of the road and we hear a car passing. There is no dip or jolt in the sound we hear when the sound goes from one side to the other side. Judging by what we hear, we would not know that the processing passes over from one side to the other.

These are just two examples of how the brain coordinates and synchronises the two sides. We initiate our speech on the left side, but then we add intonation to it from the right side, in perfect harmony, just as the two sides work together to ensure sounds move smoothly from one side to the other. We take this function for granted, but we can see from the uncontrolled movements of new born babies that it is something that we have to learn and practise.

Vision, sound, touch, movement and balance all use processing spread across both brain halves. Therefore for all these senses it is critical to coordinate, synchronise and eventually join the information flow together in a structured and meaningful way, that helps us make sense of the world around us. In the first few years of life we make great strides in synchronisation the two sides of the brain and by the age of three most children will have mastered the basics.

When this coordination and synchronisation process is delayed or not fully developed, then we can notice the effects in abilities and behaviour. Poor fine and gross motor skills are easy to observe. Poor synchronisation of the visual system may lead to moving letters, slanted lines or the need for coloured glasses or overlays. In the auditory system this may lead to hypersensitivities or poor sound discrimination, which in turn will affect attention and concentration.

By providing fast and unexpectedly changing auditory input through headphones, with a constantly changing stereo image, the auditory processing centres have no choice but to start working better together in order to make sense of this unusual input. This workout for the brain helps to speed up decision making, improve sound discrimination and reduce sensitive hearing.

Surprisingly, the effects of this kind of auditory activation do not only impact on the hearing. We have also seen many striking examples of improvements in balance. That could of course be due to the fact that our sense of balance, our vestibular system, forms part of our inner ear and is thus in some ways linked to our hearing system. More surprising is the fact that any of the other senses may also be affected. It is not unusual to observe changes in eating habits due to the fact that the sense of smell or taste has changed. Interesting for Dyslexia in particular, we often notice changes in the way visual information is processed. It may be that coloured glasses or overlays are not needed any more, or that printed text is seen much clearer, without movement or distortion.

Activating specialised functions

The adult brain of a human weighs about 1.4 kg (3 pounds), and in relation to the size of our body, is much bigger than what would be expected compared with other creatures. This large size does pose special problems for an effective communication between the two sides of the brain and this is probably the reason why specialised centres for specific processes developed in the human brain. By processing certain tasks on one side of the brain only, and in a concentrated single region of that brain-half, it is possible to dramatically reduce the distance signals need to travel and thus speed up the processing.

Of particular interest is the processing of language and speech. For the majority of people this is exclusively done in two small areas in the left side of the brain, one for language understanding, the other for speech production. The development of speech and language is unique to humans and sets us apart from all other creatures. It also forms the foundation of our educational system, culture, and social system.

But humans didn’t just stop at acquiring language and speech, as they then developed a method of recording their speech, and with it their thoughts. No, I’m not talking about records, tape recorders or MP3 players - they came much later. I’m talking about the written language, writing and reading. This allowed for much more accurate and efficient transfer of knowledge from generation to generation. And even today, despite all new technological advances, the written word continues to form the foundation of our communication and development.

Reading and writing are closely intertwined with hearing and speaking. When we listen to someone speaking a language we understand, than certain specialised parts of the left brain half get activated. The same parts also used when we read or write. It is the same with speech. When we speak, we use certain parts of our left brain, and again these are also involved when we read quietly to ourselves or write.

People diagnosed with Dyslexia often use the less efficient parts of the brain for their reading and writing which leads to either slow reading or many mistakes. The ears are the ideal receptors to use to reach the specialised language centres in the brain. We can also use the ears to keep those parts of the brain that should not be used for reading and writing busy, for instance by sending music to that side of the brain.

Depending on the specific difficulties encountered in reading or writing or the type of Dyslexia, it may also be useful to slow down the speech to make it easier for the person the decipher fast or short sounds. By giving the brain more time to process those sounds, it can learn to understand more and with greater ease. Then, by speeding up the speech step by step, it is possible to train the brain to process faster and faster, until normal speech no longer represents a barrier to understanding.

Strengthening ear dominance

Earlier on I outlined the importance of ear dominance. In general I prefer right ear dominance, as the signal from the right ear goes straight to the left brain half where the language centres are located. I myself actually have a left ear dominance. Fortunately it does not seem to impede my ability to use language or to speak fluently. However, if someone has some form of language delay or difficulty or a speech impediment, then ear dominance may play a role in that.

Reading and writing is so closely related to hearing and speech, that it is highly recommended to test for ear dominance when there are concerns in that area. Whilst it is quite easy to check for hand, foot and eye dominance, this is somewhat more complicated for ear dominance and in general specialist help will be required to test this.

In my early twenties I could often be found in recording studios, mixing the sound of pop groups. All records at that time were already in stereo, so I had to learn how to mix the various instruments and microphones into two output channels to create a rich sounding sound-scape from far left to far right. One thing I learned during this period is that if the very first sound of the recording comes from one side only, for instance through the right channel, then throughout the recording it will sound as if the right is louder than the left, even if technically both channels have exactly the same level. This is a trick the brain plays on us, a psycho-acoustic phenomena. So I would either ensure that both channels started at exactly the same time, or bring the volume up a bit on the second channel to counteract this effect.

This is one of the ways that we can signal to the brain which ear to concentrate on. By using slight time delays between the left and right channel, the brain will detect which ear is most important. In addition to time delays we can also use phase shifting and directional movement in the sound signal to encourage the brain to strengthen ear dominance to one side. By listening for a concentrated period of time to specially processed music that apply these techniques, the brain acquires a habit of using that ear in preference over the other ear. We have measured ear dominance in thousands of clients, both before and after a period of listening to this kind of music and we can testify that the ear dominance can indeed be shifted

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