Optical ‘Illusions’




Below, you will see pictures which show, when you think about them, that seeing is a very creative process in which the mind is very actively involved. The pictures prove that we must study the mind when we want to understand what and how we see. Very much  the same is true with regard to language, even on the level of linguistic sounds. If we want to understand what we hear when we listen to speech, we must again study the mind rather than only our articulatory organs, our ears, or the sound waves we produce and process.



1. The ‘blind spot’


Move close to the screen. Close your left eye, and with your right eye keep staring at the X, while moving away from the screen. At one point, the o to the right will cease to be visible. If you keep moving away from the screen, it will become visible again.  What this little, but impressive experiment demonstrates, is that there is a spot on each of our retinas which is not covered with photoreceptors, and on which we don’t really see anything. This spot is where a bundle of nerves leaves our eyeballs, for which it has to cross the retina. What is puzzling is that normally we do not see that we don’t see on our blind spots. This is because our minds must actively replace the missing optical information with hypotheses about what we should see. In our case, this is just more of the background colour of the screen.










2. Just lines

Here is a different case: if you come to think of it, the picture below consists of nothing but a few black lines on a white background. Of course, it is also two dimensional, as pictures go. Nevertheless, what we see, when we look at the picture, is a house, a cow, trees, a pathway, as well as hills in the background.  We see the cow in front of the house, although, in another sense, it is below and to the left of it. - Again, the point is, that what we think we just see is typically the result of our interpretation, and how that interpretation occurs, is a very fascinating question to pursue.



3. The famous Necker Cube

This case is famous. The picture on the screen is two-dimensional of course, but not only that, it is also ambiguous in that, when your mind interprets it as three-dimenional, it will 'decide' to either see it 'from below' or 'from above'. What is crucial here, is that this information is not 'in' the picture, but in the eye, or rather 'the mind' of the beholder.



4. Another cube:

What the next two pictures demonstrate, is once again how active the mind is as an interpreter of visual information. In the first picture the individual bits are normally seen as a two-dimensional pattern of six (partly deformed) y's, and 2 arrows. When six parallel lines are added (picture 2) the y's and arrows suddenly appear to form a straightforward cube.



5. An everyday counterpart of example four.

There doesn't seem to be much of any illusion hidden in the picture below. But think of it: your mind needs to contribute knowledge when it interprets such pictures. As far as the visual information in the picture is concerned, it might just as well represent four unrelated parts, or might it not?



6. Another Face

Here is a paradox for you: when you see this pattern well, you won't see much in it. However, as soon as you half-shut your eye-lids, the picture may become blurred, but at the same time will make more, rather than less sense. This may mean that where the eyes fail us, the mind takes over. And more often than not, this may prove very helpful.


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