What is CVI?


Attention & Its Calibration

Dictionary DefinitionDictionary Definition

Attention is much more complicated than this dictionary definition, it involves a complex set of processes including vision, or visual attention, and hearing or auditory attention.

Attention has been explained in many different ways by many different people, and the theories are open to debate and the subject of many ongoing research projects.

Introduction Example

Version 1
Jenny is walking in a park feeling happy, calm and relaxed, when she hears the sound of dogs fighting, this sound she has learned to associate with danger. She is now slightly anxious and definitely alert - she may act, for example change the direction she is walking in, or run. Jenny's systems of attention are alerting her to protect her. More alert, Jenny's attention is focused on the sound, and she may be hearing it more loudly and clearly because she feels anxious. This is a reasonably typical reaction for a person who does not have CVI.

Hearing the barking dogs alerts Jenny to possible danger.Hearing the barking dogs alerts Jenny to possible danger.

Version 2
Jenny has CVI and hears a noise she doesn't understand. It's not dogs this time but ducks quacking and squabbling over bread thrown into the water by another child. Jenny doesn't know what the sound means, nor how far away it is, nor where it's coming from. Yet she knows that with this sort of sound, things can loom out in front of her or bump into her and hurt. So the noise makes her feel very frightened, and Jenny throws herself onto the ground and goes into a tight little ball, to protect herself.

On hearing what was actually ducks, Jenny throws herself onto the ground, terrified.On hearing what was actually ducks, Jenny throws herself onto the ground, terrified.

Jenny had not learnt what ducks quacking sound like, so the experience of hearing it alerts and frightens her, because she can't see nor co-locate the ducks with the sound, so can't know what it means unless helped to learn. For other children in the park who do not have CVI, they have learnt through experience that the sound of quacking is safe. They can see and identify the ducks. They can see where they are, and can co-locate the sight with the sounds. Their attention systems give this known experience a ranking of mildly distracting, but not terrifying as it is for Jenny.

Although Jenny's story is not real, it reflects stories we repeatedly hear about people with CVI reacting atypically in a wide range of situations. One example we shared in our Looming section was Mary, an adult with CVI, being terrified of a bin.

Seeing only parts of a scene, and not knowing where the sound is coming from, means that children like Jenny

  • can't understand that there are ducks nearby and that they quack.
  • can't locate the source of the sound
  • can't identify the sound

and this is frightening.

This type of problem affects many people with CVI, and relates to why so many children with CVI seem terrified of the unknown world, and so need to wear headphones to block out sounds, or have an iPad pressed against their face to block out the visual world.

This section seeks to explain this issue, which we have called Attention & Its Calibration, to separate it from the enormous overall subject of Attention.

We have placed this in the Home section because at the end (below) we will share practical tips and strategies across five broad areas covering ways of managing the 85% of time outside of school / work, that is:

  • 1. Time at home and in the garden
  • 2. Night time / sleeping / not sleeping
  • 3. Trips (e.g. shopping, play parks, sports, parties, outings)
  • 4. Car journeys
  • 5. Socialising and visits to friends & relatives and holidays

So hopefully Jenny can in future, enjoy her walk in the park and not feel terrified at every unknown sound.

Why is Jenny so frightened?  With understanding, Jenny can be taught to tell the difference.Why is Jenny so frightened? With understanding, Jenny can be taught to tell the difference.

This is hard to explain, because every element is interconnected and affects every other element, so it's difficult to know where to start. You may have to read through this, then re-read it.

We will start by explaining three concepts:

  • 1. Sensory Radar
  • 2. Attention Calibration
  • 3. Conscious Attention Zones

Then give these with several explanatory examples (in the following subsection). At the end, you should understand why Jenny reacted the way she did to quacking ducks, and with this understanding hopefully be able to apply it to people you know with CVI, and help them.

1. Sensory Radar

Think about the computer or device you are reading this on. It probably has anti-virus software programmed into it. This software is running all the time in the background, and checks everything for possible threats. If something triggers the anti-virus software it normally tells the user with a pop-up box, alerting you to the threat, and giving you an option to ignore it and carry on, or take an action like shutting down a web page or stop running a programme.

Computers use anti-virus software as part of their systems of attention, to alert them to dangersComputers use anti-virus software as part of their systems of attention, to alert them to dangers

Our brains come installed with similar programmes to protect and help us.

Like the anti-virus software, think of the programme in the brain as a radar, running behind the scenes of what you are doing and where you are, constantly locating and checking all incoming visual information, and every sound, smell, taste and touch. Just like the anti-virus software, if something is deemed

  • unusual
  • different
  • interesting
  • a potential threat
  • harmful

the brain sends its own version of a pop-up message, we sometimes call this a pop-out and discuss the pop-out effect in several places. Pop-outs can vary in magnitude from an awareness of a familiar scent worn by a stranger as they pass you, to a threat thought to be so significant that you brace yourself and cover your head for protection. We will explain more about the different levels of alertness we experience, in the section 3. Conscious Attention Zones (below).

For simplicity, we are going to use the term sensory radar for this system of attention, that like a combined radar and radar-operator, is not only scanning, but is also interpreting.

Our sensory radar works across our five senses and surveys:

  • What is visible (seen)
  • What is audible (heard / noise)
  • What is what is felt (tactile / touch)
  • What is smelt (olfactory)
  • What is tasted

But it is seriously clever, because it covers two levels of consciousness.

1. The conscious level is easy to understand, everything you can see, hear, feel, smell and taste right now your sensory radar has picked up for you and alerted you to. We can call this the conscious sensory radar.

2. Your sensory radar also non-consciously monitors what is being seen, heard, felt, smelt and tasted.

Sensory Radar - our combined conscious and non-conscious surveillance systems constantly checking everything that is seen, heard, felt, smelt and tasted.Sensory Radar - our combined conscious and non-conscious surveillance systems constantly checking everything that is seen, heard, felt, smelt and tasted.

To try to explain your how your sensory radar covers what you are experiencing through all of your senses both consciously and non-consciously, we are going to ask you to try a little exercise:

Sensory Radar Exercise

Looking straight ahead, move your arms to the sides at right angles and wiggle your fingers - still looking straight ahead, if you are not aware of your wiggling fingers slowly bring your arms to the centre until you are aware of them. Where your fingers are wiggling are the left and right extremes of your visual field - still looking ahead, aside from the awareness of your wiggling fingers, what can you see at the extreme edges of your visual field - not much, and not anything clearly, but by immediately detecting and characterising peripheral movement your unconscious sensory radar has got that whole area covered. Whilst reading this, if a spider crawled across the desk from the far right, your non-conscious sensory radar would pick it up long before your conscious sensory radar. The wiggling fingers test came from our Visual Fields - Where Are They? Section.

In our Cerebral Auditory Impairment (CAI) section we shared the following account from a parent:

Today I was walking in the woods and I heard a woodpecker and I tried to locate the bird. As I tried to search the dense woods I realised how difficult this was. Might this be what simultanagnosia is like when visually searching in a cluttered environment? Part of me wanted to give up, thinking I'd never find the woodpecker, but mindful of my son's challenges, and encouraged by the drumming of the woodpecker, I continued to search. As I was standing I realised I had been missing all the other sounds that were present, that I had completely filtered out. The background hum of traffic from a nearby busy road, aeroplanes passing overhead, many different birds, all singing away, and a woman calling her dogs.

This person's unconscious sensory radar had all these other sounds covered. Right now, stop and think of all the noises around you - maybe the hum of a hard drive, someone talking in the background, a clock ticking, traffic outside, footsteps in the hallway. You might not have been consciously aware of all these sounds until just now, but your unconscious sensory radar had them all covered too.


  • Can you feel your hair on your face or head?
  • Do you wear glasses, can you feel their weight or where they touch the bridge of your nose?
  • Can you feel your clothes? Can you feel the weight of the cloth on your skin?
  • Can you feel your shoes?
  • Are you wearing jewellery, can you feel the ring on your finger?

For most of us, we are unaware of the feeling on our bodies of most the clothes we are wearing, or glasses, jewellery, even the hair on our heads, all tactile feelings unless we focus. If we really think about it, then sometimes we can focus on a touch sensation and become aware of it - are you wearing socks - can you feel them? Maybe a tight waistband or that itchy label you are aware of, that is your conscious sensory radar, your unconscious sensory radar has the rest covered.

Smell & Taste
Similarly, our conscious and unconscious sensory radar surveys everything that is tasted and smelt.

Why do we need sensory radar?

At its most basic level our sensory radar is designed to protect us. As hunter-gatherers we would have needed to be alert to threats, with any movement or unexpected noise quickly drawing our attention. A serious threat would have activated our 'fight or flight' response, and triggered a quick choice:

  • Fight - and blood would be directed to the fists for battle
  • Flight - and blood would be directed to the big muscles in our legs to RUN!!!!!

However, some order is required, otherwise we will want to fight or run away from everything we experience, be it barking dogs or quacking ducks.

What you are consciously aware of from your sensory radar we are calling conscious attention.

What you are not consciously aware of from your sensory radar we are calling non-conscious attention.

As with everything in the brain, there is a range, and not two neat boxes of conscious and non-conscious attention, and between the two extremes there are an infinite number of levels. We have chosen to use only two categories to keep things simple.

We will be using the following terms below, if the meanings are unclear please re-read this part again.

  • Sensory Radar (simultaneously surveying both our conscious and unconscious environment across all the senses).
  • Conscious Attention
  • Non-conscious Attention.

2. Attention Calibration

Everything our sensory radar picks up it awards a status of conscious or non-conscious.

Things it thinks we need to know about, like the smell of burning or a knock at the door, it alerts us by positioning that information in our conscious attention. (Things that it doesn't think we need to know about, like passing traffic, it actively but non-consciously ignores, without our knowing. That's a lot of - at risk - background computing!)

So things we don't need to know about, like the clock ticking or weight of spectacles on one's face, are given a lower status, and are left in the background.

This is what we mean by attention calibration, a sorting and sifting system where everything experienced is given an order somewhere between deeply unconscious to very alert.

The calibration system operates using intelligence from two different sources of data that work side-by-side:

  • a) Instinctive
  • b) Learnt

a) Instinctive

Our sensory radar is 'hard-wired' to give certain experiences an immediate conscious attention status. This probably goes back to our hunter gatherer days and is designed to protect us. We have called this intelligence instinctive, and it includes things that:

  • Move / Move Fast
  • Are bright / bright lights
  • Are loud or noisy
  • Have a strong smell or taste
  • Unexpected touch
  • Things that are unknown (see b) Learnt, below)

When any of the above are experienced, it is difficult for them to be ignored as they are given our conscious attention.

b) Learnt

Things that are unknown will include most new experiences, if we see something unusual it is hard not to look, because we are hard wired to look.

Whether it seems rude or not, our attention is hard-wired to look at anything that may seem different, out of place or unusual.Whether it seems rude or not, our attention is hard-wired to look at anything that may seem different, out of place or unusual.

Critically, we also learn what is not so important or interesting, and all these things remain there in the background, in our non-conscious attention. And here is the challenge with CVI, that word learn.

On our Access sections we explain the challenges of learning for people with CVI, which requires the effective repeated cycle of:

  • An experience, that is...
  • Remembered, so that when experienced again it can be...
  • Recollected

However, with CVI there is a particular issue around the experience bit - because for learning, the experience first needs to be consistently locatable and perceivable, through one or more of the five sense, and we know that CVI is not just about low, reduced or absent vision. Marked CVI affects all aspects of the person's existence across all the senses.

So what happens to this calibration process if the learnt intelligence (feeding the system in the brain that decides if something is important enough to warrant conscious attention, or less so, only needing unconscious attention) is unreliable or inconsistent, as is the case for many with CVI?

What happens is children with more marked CVI can't tell the difference between the threat of a barking dog and quacking ducks, because they can't co-locate the sights and the sounds, and so, can't learn from them in this way. Due to her CVI, Jenny has not been exposed to ducks in a way that she could learn what they are, where they are, what they sound like and that they are fairly safe to be around. To Jenny the sound of the ducks is a loud unknown noise from an unknown location, so it gets her conscious attention, and of course frightens her because it 'might be risky'.

Just because something has your conscious attention, as the quacking ducks clearly do for Jenny, it does not mean there is a cause for alarm. Simply reading these words is using your conscious attention.

Our conscious attention can be split into three broad zones (below)

3. Conscious Attention Zones

How are you feeling? Right now?

  • Calm?
  • Relaxed?
  • Confused?
  • Irritated?
  • Impatient?
  • Interested?
  • Focused?
  • Angry?

If you had to put how you were feeling right not into one of the flowing zones, where would you put it?

Now think why you are feeling that way?

There will be a number of different reasons affecting the way you are feeling, and one of them is from the real-time information your sensory radar is feeding to your brain processing systems.

If your sensory radar picks up something it considers particularly threatening, it trumps everything else - your sensory radar holds the ace in the pack, and if needed it can trigger fight or flight, as we explain in the Baby Monitor example.

Attention Calibration & CVI

1) Experiences

There are two different ways CVI affects how our sensory radar calibrates what it processes through our experiences, the first is to do with the actual experiences.

Taking vision alone, our sensory radar will alert us when:

  • something moves
  • something is a contrasting different colour
  • something is very bright
  • something is visually 'out of place'
  • something is interesting
  • something is different
  • someone is recognised
  • there is a change in someone's expression, suggesting a change in emotion

But a certain amount of functional vision is required for this to be effective. And as we know, with CVI:

  • Visual information can be reduced or absent due to low vision
  • Visual information can be inconsistent, unreliable and thus untrustworthy
  • CVI can affect how we understand and process what we hear, making auditory information inconsistent, unreliable and untrustworthy (see cerebral auditory impairments)
  • CVI is not just about what is and is not seen, it affects everything we experience, thus everything experienced is potentially inconsistent, unreliable and untrustworthy.

Thus, not just everything that is visual, but with CVI everything that is experienced across the five senses potentially is feeding incorrect, unreliable, untrustworthy and thus unlearnable information into the intelligence system, which decides whether something should be calibrated consciously or non-consciously - so what happens?

What happens is things are not calibrated as they should be, and too much information gets passed to conscious attention for analysis, which can be completely overwhelming. Try to see how many things you can attend to in your conscious attention at the same time.

Some people can multi-task and do several things at the same time, like listen on the telephone whilst reading and drinking a cup of coffee. To achieve this you must be giving conscious attention to a degree to all three, but by attempting all three at the same time, your capacity to focus on any one is reduced considerably (try it).

That is only three things. We think that for the person with CVI, often an overwhelming amount of information is given conscious attention, which means it is all fighting with each other, so at the extreme end of the spectrum...

  • life can feel completely overwhelming
  • learning may be near impossible
  • affected children are extremely vulnerable to real threats

This is why we recommend tents to everyone with these difficulties, because the sensory radar in a tent has very little to do, there is just a single colour to process, meaning your conscious attention is released to focus on... whatever it is you actually want to focus on.

Give the brain a break in a tent.Give the brain a break in a tent.

2. Learning

It's a challenge when calibration of attention needs learnt information.

Jenny had yet to learn that quacking ducks are safe and not scary.

Together, the challenges CVI creates by distorting (as explained in Home) what we experience through the senses, with the challenges CVI also creates as a barrier to learning (as explained in Access) it is no wonder that the calibration system is poor, and many with CVI find it hard to cope:

  • In places they don't know
  • With people they don't know
  • If anything changes or is new

And in turn can appear:

  • Obsessive - because I can't help being frightened by things
  • Aggressive - because I think I am being attacked
  • Impulsive - I have little control over these reactions
  • Unreasonable - I am trying, but I know from every past experience that this is going to be awful

So we have a problem, but there is a solution.

Using our simple model, make the experiences:

  • Perceivable
  • Meaningful and
  • Motivational

And over time, because the experiences have been made learnable, the person will remember and recognise them, and learn them, and eventually they will be correctly calibrated.

That's it, that's all you have to do - make experiences and learning learnable.

To see some examples that explain these ideas, click Next at the bottom of this page.

The 5 Areas

1. Time at home and in the garden

Home is likely to be one of the places the person with CVI knows best. The people and surroundings will have been repeatedly experienced, learned and well known.

Home can also be the place where the person with CVI is most resistant to anything new, because it may be one of the few places where they feel completely safe. This is because what is learnt and experienced has been effectively calibrated, and mostly awarded non-conscious attention, allowing the person to relax.

If there are changes to the house, or new people, they can take time to learn, and be frightening. Try:

  • Involving the person with CVI in any changes, for example if you move a room around, do it while they are in the room, otherwise they may think the room has simply disappeared and been replaced with an imposter (we share many accounts in our Safe Places section).
  • If there are visitors to the house, try not to overwhelm the person with CVI, ensure they have sufficient space and can choose whether or not to engage.
  • If you are de-cluttering (as we strongly recommend in our Clutter section), do it a bit at a time.

If a few simple rules are followed, it is likely the person with CVI will start to enjoy little changes - including meeting new people and exploring new additions to the home and garden, but remember KISS - to keep it slow and simple.

2) Night time / sleeping / not sleeping

Attention & its Calibration is likely to be an issue where the unexpected might arise, assuming the person with CVI has a consistent bedtime routine.

Think about something as simple as dreams and nightmares.

For one without CVI it is normally clear when one awakes from a nightmare or dream.

With CVI, where the world as it is, is not replicated accurately across the senses by the brain, (for some to the point where the real world and world created in the brain may bear little resemblance, see Home) - is it so clear?

For a child who cannot talk, who may not have had dreams explained to them - might they seem to be an alternative reality?

Might this be a reason why so many children with CVI are such terrible sleepers?

These are questions we ultimately can't know the answers to, but we can suggest a few approaches.

If a child wakes in the night, try to find a clear way to teach them what is real and safe. Have things in the bedroom that are very easy to find and recognise, and so can be learnt by the child, ideally available to them (safely) when you are not there.

Given a well shaded touch light (preventing light gazing), with variable settings, some children can learn to have control of their own lighting.

Try not to move things around too much in the child's bedroom, this can make re-learning, and re-calibrating more difficult.

There are many different reasons why many with CVI have difficulty sleeping, but by ensuring the environment the child is in is known, that it is familiar and is experienced as safe, helps the child to relax, because this means minimal unnecessary conscious attention needs to be awarded, and relaxed children sleep better.

3) Trips (e.g. shopping, play parks, sports, parties, outings)

This can be one of the most challenging areas. The approach for everything follows the same simple steps:

  • Remember how the person learns, and that experiences need to be perceivable, meaningful and motivational (see Access)
  • Remember many with CVI can only process a small amount of information at a time (see Gordon Dutton's blog 19)
  • Use the person's memory, and add single elements, that can be repeated and remembered, to build up understanding. (see Zoom In Zip Up Zoom Out section)
  • Use consistent words to match moment to moment experience - use language! Even with the most complex children (see Jenny and the ducks below, section on language to follow).
  • Remember the person may be feeling frightened, stressed or apprehensive, so they must not only feel in control, they must be in control.
  • Take baby steps (see Gordon Dutton's blog 15) - with baby steps you can conquer the world!

Let's revisit this by looking at Jenny and the ducks in the park.

Jenny, to enjoy the park, needs to understand what ducks are, but putting her amongst flapping noisy ducks is going to be frightening, so we need to start where Jenny is, which is to have no understanding of ducks, as her visual impairment can distort everything she experiences.

Start with one thing, maybe the sounds the ducks make, like on this video (but just listen to it first - one thing at a time)

Video Link: https://www.youtu.be/m0EuUjqBM1w

And give the word 'duck'

Then think of other ways Jenny can get to learn more about ducks, but it has to be meaningful and true to actual ducks - so for someone with a visual impairment, a fluffy duck probably isn't much like a real duck at all (unless it quacks).

Stroke feathers, if models with feathers are available, stroke that, possibly a quiet petting zoo (if uncluttered and not busy) may let Jenny stroke a duck, and even feed it, and feel the completely different sensation between stroking a duck, and a duck snatching food out of your hand. And if reinforced with great patience, over time, Jenny will not only not be frightened of the ducks, she will be bringing a bag of bread to feed the ducks, and has learnt a new word (even if she can't say it).

4) Car journeys

Being inside the car, like inside the home, is likely to be a well known experience, sitting in a similar place in a similar environment, and is probably why so many (but not all) with CVI like car journeys, because the sensory radar correctly calibrates the environment and usually awards non-conscious attention status, allowing the person with CVI to relax.

When unexpected and unknown things happen in car journeys, these can be frightening, especially noises, including roadworks, loud motorcycles and emergency vehicle sirens.

If someone is available (not the driver!) to comfort the person when this happens, over time this can help them learn that the sound can't hurt them. It is almost impossible to re-calibrate these sounds into our non-conscious attention for any of us, but without CVI, whilst alert, we are rarely if ever terrified.

Sometimes distractions can help if there is no help available in the car, like singing a favourite or funny song loudly. Sometimes alas, things happen that can't be avoided, like getting stuck in traffic with an ambulance trying to get through with sirens screaming out. As soon as it is safe reassure the person - even though the sound has passed, the person with CVI may still feel the threat.

Some parents have recommended wearing comfortable head phones listening to favourite music, to cut down external sounds. Another suggestion is wrap-around dark children's ski glasses which cut down visual distractions and frights, as can window shades.

5) Socialising and visits to friends & relatives and holidays

As we have explained, anything that is new needs to be learnt over time to be calibrated effectively.

Holidays and trips are short, which makes this challenging.

To help, take a tool kit of items and strategies you know will help the person - we explained this and made some suggestions in Protective Shields.

This kit has to be relevant to the person, but will include familiar known things (that have already been calibrated) and even out of the context of their usual environment, they should offer some comfort.

Please click next (below) for several examples explaining how the calibration of attention can be affected by CVI.


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At CVI Scotland we are devoted to helping people understand cerebral visual impairments, and together working towards developing the understanding of this complex condition.