Posts Tagged ‘senses’

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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Long ago I read a newspaper article which beautifully praised the life and works of a famous artist.  I have forgotten his name but that is of no consequence, for similar articles appear from time to time describing such clever people.  What struck the writer of the article most strongly was the ability of the artist to visualise ideal scenes – the sort that idealise Nature to a seemingly impossible degree.  Thus it was that he could paint a scene (real or fictional) not as it would normally appear, but as it seemingly ought to be if only the faults and vagaries of Nature were removed or rectified.  But perhaps that, in itself, was not the true genius of the artist ; rather, his genius showed itself in what he described as the perfect clarity of his visions, and in his wonderful ability remember and to paint exactly what he saw.

I expect there are many artists who share this gift in some measure ; and many more people who have the vision but lack the artistic skill to reproduce it.

And I expect there are just as many who have the visions (and maybe the artistic skill) but of a kind that are not at all beautiful – visions of perfect awfulness.  And it may well be that just about everyone has had such visions (both beautiful and horrid) in dreams.  Perhaps the great artists manage to enter into a dreamlike state whilst remaining fully awake.  Those with experience of hypnosis will have a good idea of what I mean.

One also hears occasionally of people who experience vivid impressions of scents and tastes, and even bodily feelings such as tensions and pains, though these are not so easily conveyed as art.

So four of our senses may be directly and vividly stimulated without any involvement of the organs of sense.  And generally this is accounted a good thing, a mark of genius.

When we turn to the fifth sense we find, first, something similar.  For example, it has been said that Beethoven could hear an entire symphony before he even set pen to paper or toyed with his piano keys to confirm his hearing.  Perhaps his profound deafness sharpened his imagination, but I don’t think that wholly accounts for his ability here, for Mozart also had the gift or genius.

I suspect also that great poets may vividly hear their lines before they begin to write ; as if their muse (or genius) is instructing them on what to put on the paper ; so as to ensure that the sounds, the rhythm, the rhyme, the metaphor and the meaning are all quite perfect for the context.  Again all this is generally marked as a gift of great price.

But then, the general opinion changes markedly in a certain respect.  For if the person who hears the voice in his head is not an acknowledged literary master, then his voices are taken to be signs, not of genius, but of madness.

There only so much that might be written about many things in the world ; but when it comes to people, the possibilities for discussion are endless.

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People are constantly talking of reality.  How often do we hear words such as : “get real” : “the reality is” : “it really is true”.  It is as if we believe that the human senses and the human mind possess a mystical quality that enables them to transcend the material world and take a privileged view of it.

But is it true that human beings are capable of perceiving reality?  Might it not be case that a herring has a better, truer appreciation of the world than we do?    Are we wise to assume that the size and complexity of our brains has made us better at perceiving?  Is it possible that all our complicated vocal expressions that describe the world are merely noises without any particular meaning?  Might it not be the case that our consciousness is simply an elaborate deception – an evolutionary accident that is leading us to a dead-end?

There is so much to ponder here.  And we will not be the first to ponder it, for certainly the world’s great religious thinkers have given much thought to the matter since the very earliest times.  In fact, most likely, it is with this pondering that religion began.

It is interesting to reflect that, if we did perceive reality, we could never make a mistake about what we see.  We could never mistake one person for another or one thing for another ; we could never mis-hear somebody’s words.  Also, if we did perceive reality, there would be no science being done today ; all knowledge would have been completed long ago.

But, as ever, there are other ways of looking at the matter ;  and some of those ways offer hope to those who believe that reality is within our grasp.

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People talk about space as if it were the most obvious thing in the world.  But is it?

When one looks into the night sky, one is aware of a multitude of points of light.  Because were are able to separate these points of light into separate objects, we say there are spaces between them.  We go further ; we say that we can see the spaces.

But, suppose there were no stars in the sky?  Take them all away, and what would one see?  Nothing.

It seems that space is not an object that can be seen, heard, felt, smelt or tasted.

So, what is it?   It is something we infer by virtue of it’s being unavailable to our senses.   It is surely a product of our imagination.

Likewise for those unsensed things that people believe exist in space – atoms, electrons, quarks, fields of this and that.  All are products of human imagination – and often of highly trained imagination.

But is space, and all the invisibles that are in it, real?  I see no reason why not, although our understanding of them might need adjusting in the light of future disciplined imaginings.

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