Tuesday, October 19, 2010

Curiouser and curiouser

I watched Horizon last night on the BBC. The programme was called 'Seeing is believing' – except that it is not. Apparently our senses can be fooled – or sometimes act to fool us. The programme makers didn't use the words, but the sub-text seemed to be that 'reality' is an illusion created by our minds. Colour isn't real, but contextual – what we perceive as one colour is influenced by the other colours near by. Taste can be affected by vision – putting red food dye into lime flavoured water can make it 'taste' like berries because that is what our mind expects. What we hear can also be affected by what we see. The makers showed the 'McGurk' affect – if a person makes a 'ba' sound, while making the lip movements for 'va', a person looking at them will always hear 'va' – even if they know about the effect! They did a split screen on it and it was surreal – the sound was the same, but if you looked left you 'heard' the sound as 'va', if you looked right you heard it as 'ba.' The eyes over-ruled the ears.

More, sometimes our senses are only guessing – we take in so much information at any given moment that it is impossible for our brains to process it all. So the brain is selective. It edits. It chooses what it thinks is important. And so we can end up 'seeing' what we expect to see. That's how a lot of magic tricks and illusions work. If the magician tosses a ball up in the air twice, we 'see' it go up the third time, even though it doesn't – and when our brain catches up with reality, it seems to 'vanish' in mid-air.

Sometimes it essentially makes things up, find patterns where patterns don't exist. Remember the 'monsters' in your bedroom as a kid, that turned out to be shadows, or a pile of clothes, or an odd assortment of toys? That was your brain guessing – making a pattern out of nothing. This was a useful trait when we were evolving – if the thing that looks like a tiger in the woods is a tiger and we run … well, if we're wrong, no harm done; if we're right, we may have saved our lives.

And we're not necessarily limited to our five senses, or using them only in the traditional way. They had a blind man cycling a bike, navigating using echo-location. He can build up a 'picture' of his surroundings using tongue clicks – the scientists thought that the part of his brain that might usually have been used to process visual information may have been re-wiring itself. And they had vibrating belts – no, not those kind of vibrators! - one used by pilots, tied in to their machines' sensors to give them an artificial 'view' of the ground. When they couldn't see the ground with their eyes they could still see it another way … through the intensity and location of the vibrations. Another belt acted like a compass, giving the wearer the 'pigeon' sense of being able to detect the earth's magnetic field. In both cases the test subjects quickly adapted to be able to use these new 'senses' negotiate their environment.

The scientists spoken to were all very enthusiastic about the discoveries they were making about how the human mind works and how our senses work to perceive the world around us … and rightly so. But I think it raises another interesting question. One of the big 'drums' that people like Dawkins have been banging of late is about trusting our senses – all there is is what our five senses tell us. But we don't understand how our senses work. We can't be sure of what they are telling us all the time. Sometimes we are only perceiving what we want to perceive. And in other ways our senses aren't as limited as we used to think. They can adapt. Behind what we sense, or think we sense, is mind – filtering, interpreting, knowing.

Seeing isn't believing. Believing is seeing. There's more going on than just the interaction of our five senses with the world around us. But most of us knew that already.

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