Everything you’re seeing, hearing, touching and smelling is an illusion – a show put on for you by your brain.  If you were aware of the reality of the world you’d be shocked.  Think that’s rubbish?  Read on.

In his book The Brain, American neuroscientist, David Eagleman,  gives astonishing insights into the way our brains actually create the reality around us that we think we’re experiencing accurately.  I’m drawing on those insights here.

You probably feel like you’re connected directly to the world through your senses.  But in fact, seeing isn’t happening in your eyes, hearing isn’t happening in your ears, feeling isn’t happening in your fingers and smell isn’t happening in your nose.  They’re all happening in your brain.  Eyes, ears, skin, nose and mouth too are interpreters of the outside world, passing information to the brain and translating it into electrochemical signals – the brain’s common currency.

Your brain is like the living entity inside a dalek – sitting in a dark casing – with no direct access to the outside world, ever.  It relies 100% on your senses to tell it what’s happening.

Your guessing brain

A third of the brain is used for seeing so let’s take vision as an example.  We normally think that our eyes send data to somewhere in the brain and, hey presto, we see.  The truth is much weirder.  The brain actually generates its own reality – an ‘internal model’ – before it gets any information at all from the eyes.   Your eyes are, of course, at the front of your head. And at the back of your head is your brain’s visual cortex.  Between the two is the thalamus and some of the data from your eyes is allowed through to the visual cortex.  But there are ten times as many connections going from the visual cortex to the thalamus as there are in the other direction and that’s not what you’d expect.

What’s happening is that your brain’s guessing what’s out there in the world and sending the guesses from the visual cortex to the thalamus.  The thalamus then compares the guesses with what’s coming in from the eyes and only reports back to the visual cortex if there’s a difference between the two – eg ‘I should see a dog basket here and there isn’t one’.

So what you experience as the business of seeing is less about light coming into your eyes than about projections of what’s already in your head.  When you walk down a city street, for example, your brain makes assumptions about the cars, pavements, people and buildings in front of you based on what it has learned from countless other experiences of other city streets over the years.  And it’s still refining that internal model from what this latest experience is telling it.

The world you see is an illusion

What’s actually out there in the real world is very different from what your brain tells you.  Take colour, for instance.  There isn’t any.  Not in the outside world.  There are only wavelengths of electromagnetic radiation bouncing off objects and going into your eyes where they’re ‘interpreted’ and become colour.

That’s disorientating and a bit scary.  Listen to David Eagleman:

‘Not only is there no color, there’s also no sound:  the compression and expansion of air is picked up by the ears and turned into electrical signals.  The brain then presents these signals to us as mellifluous tones and swishes and clatters and jangles.  Reality is also odorless:  there’s no such thing as smell outside our brains.  Molecules floating through the air bind to receptors in our nose and are interpreted as different smells by our brain.  The real world is not full of rich sensory events; instead, our brains light up the world with their own sensuality.’

Similarly for touch, ‘receptors on the skin (and also inside the body) convert pressure, stretch, temperature and noxious chemicals into electrical signals’.  Takes the shine off things a bit for lovers.

How many realities?

The implications of all this for what constitutes reality are significant, to say the least.  Outside our brains there’s only energy and matter.  The world we think we know is a ‘show’ put on for us by our brains and it’s likely that the show is slightly different for every person.

Given that there are seven billion human brains on the earth and trillions of animal brains, it may be that, strictly speaking, there’s no single version of reality.

Pity the police trying to reconcile witness statements.