Illusions

Do your eyes ever play tricks on you? Maybe you've seen something that puzzled you so much that you had to rub your eyes and look again?

Chances are you may have been tricked by an optical illusion.

The word illusion came from the Latin "illūsio" – deceit. This interpretation briefly, but very clearly describes the essence of this term.

In this lesson, let’s find out what is an illusion and what kinds of illusions there are.

Sure, we have five main senses – sight, hearing, taste, touch and smell – but about 75 per cent of the information comes from our sight, making it the most ‘important’ of the five senses. The vision depends, obviously, on the EYES to see and on the BRAIN to make sense of what we see.

The optic nerve at the back of the eye connects to the central nervous system in the brain. The brain receives electrical impulses (stimuli) from our eyes; but the brain adds two extra ingredients to image: memory and interpretation.

Sometimes our eyes play tricks on our brains.

Visual illusions are caused when differences occur between our expectations and the image seen by the eye.

 Physical illusions are phenomenal illusions which occur before light enters the eye, such as a mirage, a rainbow...

Physiological illusions are the effects on the eyes or brain of long stimulation of a specific type: brightness, tilt, colour, movement...

The Mach band illusion is an example of a physiological illusion. The line in the middle of the picture is one solid color. However, because of how the eye's retina filters the different shades on either side of the line, the right side of the line appears darker, while the left side of the line appears lighter.

Other optical illusions are cognitive.

Cognitive illusions, such as ambiguous, distorting and paradox illusions, occur when our brains automatically make assumptions based on the information sent from the eyes. These illusions are sometimes called “mind games."

Ambiguous illusions are pictures or objects that can be seen in more than one way. Rubin's vase is one popular example of an ambiguous illusion. Can you see both the vase and the two faces?

Distorting illusions use different techniques to make objects of similar size, length or curvature appear distorted. A famous example of a distorting illusion is the Müller-Lyer illusion.

Doesn't the line in the middle look longer than the ones above and below it? However, all three lines are the same length!

Paradox illusions occur as a result of pictures or objects that cannot exist or are physically impossible. Paradox illusions are popular in works of art, such as those made famous by artist M. C. Escher.

His Waterfall is a classic example of a paradox illusion. Do you see how the water from the waterfall appears to travel uphill before once again reaching the top of the waterfall?

Therefore, if visual illusions have existed since the dawn of mankind, what is the oldest optical illusion created by man?

Notwithstanding the lack of any written trace, the first human beings would certainly have noticed optical phenomena such as mirages, the size of the Moon at its zenith, sticks or poles which appear to be broken in two when half-immersed in water, a negative image after having looked at the sun…

One of the first optical illusions knowingly created by man is from 2,500 years ago; in some coins from the island of Lesbos, Greece, you can see the profiles of two animals facing each other, apparently herbivores such as calves or goats, which, however, form a third animal – a ferocious animal (maybe a wolf) – when seen from the front.

Surprisingly, a person loves consciously to deceive, and therefore the creation of illusions became for some people a profession that brings good money. Of the popular illusionists, the Safronov brothers can be called. Their repertoire is surprisingly diverse, and having looked at their show, you involuntarily begin to believe in miracles.

Well, an illusionist of all times and peoples without doubts can be called David Copperfield. Today he does not give a show, but in New York his cafe works, where there are no waiters - a voice from nowhere specifies the order of the visitor, and then ordered by itself materializes on the tables.

Optical illusions can teach us some important lessons about life. There is often more than one way to see things. It’s okay if you and your friend have a different opinion about something, for example. You’re just seeing things in a different way, that’s all!

Clever artists can use these tendencies to trick our eyes and brains into seeing what's not really there!

There are millions of optical illusions of different kinds. But I’d like you to have a look at the tricky and amazing illusion art works by the Ukrainian painter Oleg Shuplyak. His paintings often depict famous historical figures.

Can you guess who they are?

1. William Shakespeare

2. Vincent van Gogh

3. Nikolai Vasilyevich Gogol

4. John Lennon

5. Charles Darwin

6. Salvador Dali

7. Mikhail Illarionovich Kutuzov

8. Leonardo da Vinci

9. Uncle Sam

10. Lev Nikolayevich Tolstoy

I hope you had fun being deceived by puzzling visual challenges by Oleg Shuplyak.

That’s all for today! Join us at videouroki.net.