Sensory adaptation

When sighted people ask about being blind, they often wonder:

Is it like seeing black all the time?

My favourite conversation about this took place on the metro in Oslo. I was doing research on blindness. And the person who asked seemed to be sleeping rough. I answered, ‘No, because there is nothing there to see black with’. She lifted her index finger into the air and cut straight to the chase: ‘So, like seeing with my index finger. Or my big toe.’

Is it better to have had vision or to be born blind?

But people seem to know, intuitively, that there is no single answer to this. My response is usually: ‘It depends.’ Then people, often spontaneously, talk about recognising friends by their faces; yet they soon realise that voices are just as important – as are the skills needed to identify them. Some also talk about the smell of colours, mostly ocean blue and grass green. (See our blog for the scientific approach, the crossmodal correspondences between the senses, Crossmodal brain plasticity and empowering of sensory abilities, and Multisensory processing.)

How long does it take to adapt to being blind?

Again, my answer usually is: ‘It depends’ – on when and how vision was lost, the use of other senses before and after, and overall health. The brain must adapt to recognise sensory information without vision. And new habits take on average 66 days to become automatic. (See our blog for Decay and maintenance of sensory memories, Visual memories and sensory experiences, Reading braille in colour, and My vision, my identity.) I wonder, therefore, if it would be better to ask not how long it takes to adapt, but rather: how to adapt?

In an attempt to explore this question – how do people adapt to new sensory information? – I started brushing my teeth with my left hand instead of my right. Doing this meant adapting to new sensory information, especially from proprioception, touch, and the vestibular sense (see our blog for Growing into one’s own body). Drawing on previous research on people who have lost vision, including some of my own work, I expected to:

– Do well on my first attempt, then struggle to adapt to sensory information from my left hand

– Have slip-ups – old habits die hard – that would set me back in my progress

– Try different routines before fully adapting to sensory information from my left hand

My first attempt went well, but then came the second and the third – and they felt strange. Holding the brush was awkward, and I did not really know how to move it properly. It felt as if the brush was sliding around with no clear purpose. And I was certainly not convinced my teeth were clean afterwards, but I resisted the temptation to go back to using my right hand.

Then, attempt five – and my first slip-up. I suddenly realised that my movements with the brush were different, and next came the feel of it against my gums. Judging from the position of the brush this was my usual right-hand brushing routine, I had at least caught my slip-up early.

For the next attempt, I reminded myself – even said it out loud – to use my left hand. I was expecting this brushing to be more difficult, but I did not notice any real setback. And I wondered if this was because I had not yet formed a routine for brushing with my left hand.

young child smiling and brushing teeth
AI-generated illustration for SmartSense

To stay on track, I decided to pay close attention to what I was doing from the moment I applied toothpaste to the brush. I noticed the difference in how I used my two hands. With my right hand, I used a full-hand grip to hold the brush. My wrist was often stiff, and the pressure on my gums was quite hard. With my left hand, I flexed the brush in my grip: I held it almost as if I were holding a pen, sometimes adding my middle finger; I gripped it between my index finger and thumb, again sometimes bringing in the middle finger, and my wrist bent, stretched, and turned. The pressure on my gums was much lighter than with my right hand.

Over the next three to four weeks, I began to establish a routine for how I brushed – moving from the left upper teeth, across to the right, then down to the right lower teeth, and over to the left, before returning to the middle for an extra clean. My grip on the brush became firmer, and the pressure on my gums more constant. It no longer felt as if the brush was sliding around with no clear purpose. And I was almost convinced my teeth were clean afterwards. I had had three slip-ups, but I caught them early and carried on brushing with my left hand. It was time to try a deliberate right-hand brushing again.

Week seven, day one: return to right-hand brushing. At this point, I had a consistent routine for my left-hand brushing: the movement and feel of the brush were the same every time. Returning to my right hand was a bit of a shock. My right hand now felt inferior to my left: the handling of the brush was less flexible, the pressure on my gums was harder, and my teeth did not feel any cleaner than with my left-hand brushing. Next time, I brushed with my left hand again, without noticing any setbacks in my progress. In fact, left-hand brushing now felt more natural to me.

I have continued with my left-hand brushing, and if you asked me which hand I used this morning, I would not be able to tell you. But it was most likely my left.

My required adaptation was both minimal and reversible – only two to three minutes in the morning and evening, and it could be stopped at any time – and so should by no means be taken as representative of how people adapt when every aspect of their life has to change. For example, after total sight loss. There is also a little twist to my experience. I am “a leftie” who was trained to use my right hand. So, I wonder if my adaptation to new sensory information was facilitated by some pre-existing left-hand architecture in my brain. Still, I hope my experience offers a glimpse into how people adapt to new sensory information.

See our blog for Activities; especially 94-96.

Blog post author: Dr Torø Graven

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