The Standing Invitation

Posts Tagged ‘Consciousness

A Few Comments On Your Wallpaper

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Here’s another one drawn from Dennett’s Consciousness Explained. Before reading on, find yourself a pack of cards. Go ahead, I’ll wait.

Got the cards? Obviously you found them using your eyes. Human vision is pretty good for mammals. Reflect for a moment on how much detail you can see right now: you see a whole page of words, on your computer screen, in full colour. Probably you are aware of what objects are behind your monitor, colour the wallpaper is, what its texture is. It’s pretty impressive.

Now take your pack of cards, shuffle them and select one at random without looking. Keep your eyes focused on one point directly in front of you. Without turning your eyes to look at it, hold the card at arm’s length to one side, with the picture-side turned towards you. It’s in your peripheral vision. You probably can’t see it very clearly, and have no idea what card it is.

Now move your arm a few degrees closer to the centre of your field of vision. Can you identify the card now? Can you even see what colour it is? Move it a little closer. Black or red? Face card or number? Keep moving it closer, without looking directly at it. It really is surprising how close it has to get to the centre of your field of vision before you can confidently identify it; up till then, it’s a blur.

The clear patch in the centre of your vision corresponds with your fovea, the densest concentration of rods and cones in your retina. This is the only part of your eye that can see in detail and colour. The rest is devoted to picking up motion, change; it is the early warning system that tells you where to point your fovea.

You don’t see the world. You see a description of the world that is provided by your eyes. Your fovea flicks from one point of interest to another, gathering information with which to update your brain’s virtual-reality reconstruction of your surroundings. The brain’s editing process is seamless: it’s only when you deliberately prevent your eyes from moving that you realise just how patchy your vision really is.

Dennett goes further: imagine you have some really garish wallpaper, in the style of Andy Warhol, that consists of thousands of identical pictures of Marilyn Monroe. When you look at the wallpaper, how much of it do you really see? Every Marilyn in detail? Or does your brain just ‘fill in’ the rest, based on inspection of one or two. Either way, you can’t tell the difference.

The unsettling conclusion of all this is that you actually perceive the world in more detail than your eyes are providing. The sense of vision is not a window on the world: it is a cobbled-together bag of cheats, tricks and shortcuts. Fortunately, this seems to be enough.

Written by The S I

July 18, 2011 at 8:05 pm

Posted in Science

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You Just Think You Are

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We’re big fans of Daniel C Dennett here at the S I. This magnificently bearded Tufts philosopher has spent much of his career trying to solve the ancient puzzle of what the mind is, and how it relates to the brain. His slogan: “Yes, we have a soul, but it’s made up of lots of tiny robots.”

How is it, he asks in his book Consciousness Explained, that a collection of unthinking nerve cells can somehow go to make up a thinking, feeling being? No single brain cell knows or cares who you are. So how can the ensemble be different? What is the magic step that turns robotic components into a human whole? To try to make sense of this emergence of the self, he introduces the idea of the centre of narrative gravity.

In physics, gravity is potentially a tricky business. Consider a football. Drop a football, and any physicist will tell you it will fall. How do they know this?

It is theoretically possible to go back to first principles: calculate the gravitational attraction between all atoms in the ball and on Earth, work out the details of their interactions, then, millisecond by millisecond, determine that every atom in the ball will ultimately move downwards. But of course this is not what they do. There is a much easier way: give the football a centre of gravity. This is a single, imaginary point that stands for the whole ball. It averages out the incredible complexity of the atoms in the ball, and allows physicists to treat it as a unified entity.

Note that the centre of gravity is fictitious. Although it is located at the centre of the ball, it is not associated with an atom at the centre, or indeed any one atom. A football’s centre of gravity exists only in the minds of people who study footballs.

In the brain, Dennett argues, we have something similar. There are billions of brain cells, all firing all the time, each one telling its own story. Every time a cell fires, a set of conditions is reported – information about what a retinal cell is saying, or what the balance organs of the inner ear are saying, or what other brain cells are saying to each other. To run an efficient organism, these narratives have to be made sense of – and quickly, before the sabre-toothed tiger mentioned by one brain cell has a chance to eat you. The neurons can’t be addressed individually. Wouldn’t it be better to treat them as one thing? This is where the self comes in.

Who are you? You are your brain’s centre of narrative gravity: you are the point in space around which the experiences reported by your brain cells cluster. You, unified, singular you, are a fiction generated by your brain, as flag to rally defences around.

It is your brain cells, working together, that are reading these words right now. You, the person, are not. You just think you are.

Written by The S I

July 14, 2011 at 8:25 pm

Posted in Science

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