Archive for July, 2012

I can remember, when I was about twelve or thirteen, being told how the eyes work.  It was part of a physics lesson and occurred after we had covered optics generally.

The gist of that lesson was this.  The eye admits light, through the cornea, the lens and two kinds of liquid media, and then establishes an image of the outside world on the retina.  Due to the workings of the aperture and lens, this image is upside-down.  Thus, the brain has the task of turning the image the right way up so that we can make sense of it.  If the brain did not do this, then the world would appear upside down to us ; and this would be both very confusing and untrue.

In retrospect, I can see that Mr Chaplin told us this story because we were just beginners at the subject, and the true story would have been a very complicated diversion from the purpose of the lesson, which was optics and not cognitive psychology.

But there was a time (up to the seventeenth century) when this story, about the brain having the task of turning the retinal image the right way up, was once the authorised version of the biology of seeing.  In those days it was perfectly obvious that the retinal image was upside-down, for anatomists had actually seen it in their experiments with eyes taken from real animals.  It was therefore equally obvious that the image had to be turned the right way up again.

But George Berkeley, who was arguably the most subtle of the three great empiricist philosophers, disagreed.  He said words to the effect that, “The brain neither knows or cares which way up the image is ; and nor do the eyes.”  The eyes are merely instruments for gathering light ; the brain works with the effects of that light so as to make an image in the mind.

If that is true, however, how do the eyes work out what is up and what is down?  They must do so, because we can see ‘up and down’.  Berkeley’s answer was that the eyes naturally know nothing of up and down.  And nor is there some little man living behind the eyes who studies the retinal image and knows that it is upside down.

The eyes deal only with light.  Upness and downness are dealt with by a separate system.  He called this separate system the sense of touch ; though nowadays we call it the proprioceptive system ; the system whose nerves are sensitive to tensions in the ears, skin, muscles, tendons and bones.

It is the proprioceptive system which tells us, for example, whether our arm is moving up or down ; or right to left ; or backwards or forwards.  For example, if the arm moves up it feels heavier ; if it moves down it feels lighter.  More subtly, it informs us of every detail of our posture.

So, how is it that we are able to see and recognise whether our arm is moving (say) from left to right?  It is because the eyes learn to associate movements of the retinal image with feelings from our muscles and bones.  So, when we move our arm to the right, the retinal image of the arm moves ;  while (in synchrony with that) the muscular signals give a movement to the right.  The fact that the retinal image of the arm moves to the left is neither here nor there, because we take our primary cues on direction from our muscles, not the image in the eyes.

Similarly, when we keep our body still, and see an object move across our field of vision, the muscles that control the movement of the eyes register particular tensions which indicate the direction of their own movement as they follow the image.  The visual system takes its cue on direction from these muscular tensions.

There are a number of interesting consequences to Berkeley’s observations, and he indicated them as hypotheses ; but it was not for some two centuries that the confirming experiments were done.  In the first half of the twentieth century, several experiments confirmed that the eyes “neither know or care” which way up the retinal image is.  People were fitted with spectacles which inverted the images they saw.  At first, the world appeared very confusing ; but within hours the people could walk about safely ; within days, they could drive a car safely ; within weeks they could fly an aeroplane safely.  The nervous system simply adjusts itself to the new circumstances.

Similarly, spectacles have been worn which rotate the retinal image through various angles ; others switch left to right.  All with the same effect – the vision adjusts to the new conditions.

There is much more to tell of the path that Bishop Berkeley opened to us, but I must stop here for now.  Suffice to say that the movements of the body are vital to developing and maintaining healthy vision ; for the senses do not exist independently of each other ; they are integrated.

Also terms such as left and right are not absolute, but are relative ; but they are established by convention.  There is no homunculus (little person) inside the brain or mind who makes sure that we get orientations and movements ‘correctly named’ ; the nervous system has been so designed and established that it takes care of all that.

If there is an observer of all our sensory information, then it is not something that the material sciences may do experiments with, for it would need to be super-sensory in order to perceive its data objectively.

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Are we ready to become aware of ourselves?

I have been fascinated with the material world for as long as I can remember.  It isn’t true that young children take the world for granted ; some at least do ponder on the origins of things and their destinies.  But there was one thing that I did for long take for granted – my consciousness ; in fact, when I was very young, I did not even think of consciousness.

But what is consciousness?  It is one of those things that is not revealed to us through the senses.  Rather it is our consciousness that informs us that we have senses.

We have a difficulty in describing what consciousness is without using metaphors.  For example, some psychologists have described it as a screen on which our world is projected.  But a screen is a material thing, while consciousness is not ; and so it is a potentially misleading linguistic device, for people have a habit of treating metaphors as if they were literal descriptions.

So consciousness is not a material thing, not detectable by the senses.  And what, therefore, is its proper classification?  It must surely be spiritual ; i.e., a known real thing which is not detectable by the senses.  And it is a thing which has the thoughts of psychologists tied in knots as they ponder it.

We are in the habit of asking, “Where does a thing come from?”  We are fascinated by origins.  But where does consciousness come from?  The current orthodoxy in psychology says that it is an ’emergent property’ of the brain.  According to this hypothesis, the complexity of the brain somehow causes consciousness to arise from it.  But still nobody knows how this occurs and nobody is any wiser as to what consciousness is.

But then the idea arises, “Why should it be matter that gives rise to consciousness?”  For isn’t it at least equally likely that it is consciousness that gives rise to matter?

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