Ian Wardell
Junior Member
Originally posted by inimalist
Because of this, there are some weird experiments (optical illusions being the simplest example) where our awareness is terribly ineffecient.
You could scarcely be more wrong. So called optical "illusions" help to illustrate that what we see is actually an implicit theory about the external world. I have a blog entry here (link deleted) which might be of interest.
If it were not for optical "illusions" we would see squares A and B as being the same colour. Indeed if we were unable to perceive optical illusions we wouldn't see reality anything like as we see it now -- we wouldn't even be able to see that the world is 3D! We wouldn't be able to negotiate our environment. Indeed, although we might have perfect vision, we really wouldn't be able to see all that terribly well.
Update: OK I've just found that I can't post a link to my blog as of yet!
OK on my blog I talk about this so-called "illusion"
Further update. I can't even upload an image or link to an image either! This is just absolutely useless. Can't see me making any more entries in this place! If people are interested just go and search for the checker-shadow illusion! 😠
And to quote my blog:
I'm sure that all of us are astounded that the squares A and B are actually the same colour. It is the shadow cast over B by the cylinder which makes us think otherwise. What this suggests is a quite incredible illusion.
However I think there is a pervasive naivety about the nature of perception. Most of us doubtless feel that we see the external world directly. But we emphatically do not.
Consider a red rose. We think of a red rose as being the same colour throughout the day. However the light from the Sun reaching the Earth varies throughout the day. When the Sun is low in the sky, lots of blue light gets scattered away since the sunlight has to travel through a greater quantity of air. So if we were to passively see colours "as they really are", then the colour of our red rose would change throughout the day. Indeed the colour of all objects would change throughout the day. But in fact our rose seems to stay pretty much the same colour throughout the daylight hours. Why is this?
The answer lies in the fact that we do not in fact simply passively see what is out there. Rather the brain performs certain operations on the data coming through our senses and presents it to our consciousness in a form that we can make sense of. Everything we ever see is in fact a hypothesis about how the world is. Thus we have an implicit theory about the external world that it contains objects which have specific intrinsic colours. Hence the brain will perform those operations which ensure that objects do indeed appear to be the same colour throughout daylight hours.
This applies not just to colours, but everything we perceive through our 5 senses. In a way then everything we ever perceive is an illusion. But I think this is misleading.
Let's consider the "illusion" above again. If this were a real 3D object and we were to approach it and view it from various angles, then we would see that squares A and B are very different colours. Indeed their intrinsic colours would be precisely as we perceive them in the illusion above.
But in that case what justifies us in labelling it as an illusion? If this were a real object that we are seeing, then squares A and B are very different colours. Our senses are not deceiving us. Indeed if someone claimed to see the squares as being precisely the same colour, then it is doubtful that he could proficiently visually apprehend his environment.
This is not to say we never perceive illusions. Sometimes we seem to see something, but which on closer inspection turns out to be something else entirely. Or sometimes what we seem to visually see is not consistent with our other senses.