1. Optical Illusions

2. Hermann Grid

3. Stroop Effect

4. Kaniza Illusion

5. Most people see a triangle in front of three circles.
Your brain tries to make sense of this pattern by going for the most likely explanation.
In this case it is a white triangle in front of 3 colored circles.
Even when you know that the white triangle does not really exist, your brain still opts for it as the most likely explanation.

6. Illusions The Müller-Lyer Illusion
Why does line (a) appear longer than line (b) in this illusion?

7. The Müller-Lyer Illusion (continued)
Illusions
The Müller-Lyer Illusion (continued)
Here’s an example of the illusion in real life. The line (a) looks more like a distant corner than a near one. Since the vertical lines form images of the same length, the more “distant” one must be perceived as longer.

12. Say What!? The monsters are identical in size.
Although this is only a two-dimensional drawing, your brain looks at the contours and sees it as a three-dimensional tunnel.
Unconsciously, you are applying the rule that an object must get smaller as it gets further away.
Since the monster doing the chasing is not smaller, you conclude it must – in reality – be a bigger monster.

13. WHAT’S THE FIRST THING YOUR BRAIN SEES???
Illusions
Reversible Figure
illusions in which the same object is seen as
two alternating figures – first one then the other
WHAT’S THE FIRST THING YOUR BRAIN SEES???

16. Reversible Figure (continued)
Illusions
Reversible Figure (continued)

20. Duck or bunny rabbit?

28. Are these lines straight and parallel?
Illusions
Are these lines straight and parallel?

29. Although barely believable, all these lines are straight, and parallel to one another.
This illusion comes about because the black and white rectangles do not sit directly above one another.
You clearly see the horizontal grey space between the black and the black, and accentuate this difference.
However, the horizontal grey between the white and the black rectangles is not so clear.
Your visual system decides this space is not real, so shrinks it.
This has the effect of producing lots of wedges, which your brain puts together and decides you are looking at non-parallel wavy lines.

31. Illusions Other Illusions (continued)
Is the blue side the front or back of the cube?

32. Illusions Other Illusions (continued)
Are the circles on the inside or the outline of the image?

33. Illusions Other Illusions (continued)
Are the horizontal lines straight or curved?

34. Illusions
Other Illusions (continued)

35. How many prongs are there?

36. These shapes are impossible!
This shape is impossible.
It is impossible because as you look at this flat 2D picture, your brain automatically tries to build a 3D shape in your mind – and it can’t.
This trident makes use of the fact that a drawing of a cylinder can be made using two lines, where as a rectangle takes three.
So although throughout the trident there are only 6 lines, these can make 3 cylindrical prongs but only two rectangular ones.
Impossible shapes show how our brains automatically try to make us see in 3D. After all, the image on your retina is flat, yet everything you see has depth.