[zeroca]

I’ve chosen the name of thread randomly. The thread is about illusions of any kind, preferably with explanations.
Below is text from Wikipedia with the image, which also from there:

The Scintillating grid illusion is an optical illusion when dots seem to appear and disappear at the intersections of two lines crossing each other vertically and diagonally. When a person keeps his or her eyes directly on a single intersection, the dot does not appear. A variation of the Scintillating illusion is the Hermann grid illusion (see section below). In the picture on the right, a person should see white dots turn black and then turning white again very fast.

Can anyone offer its own explanation?

[mkirkpatrick]

Originally Posted by zeroca I’ve chosen the name of thread randomly. The thread is about illusions of any kind, preferably with explanations. Below is text from Wikipedia with the image, which also from there: Can anyone offer its own explanation?

Illusions abound, we are surrounded by them; I got spots before my eyes looking at the grid.

Kind regards, Michael.

[zeroca]

O.k. Then you remember my posts about central and peripheral visions (peripheral, i.e. field of vision). Narrow your eyes (up to very small vision slit) and look at grid only with your central vision. You will notice that effect of illusion eliminates. Even you can move (turn your head) left and right in turn with narrowed eyes and you will notice that illusion doesn’t exist.

Another way: you should fix your binocular vision on one point of grid without any little shifting of them (trying your best not to move them), but it's hard and not everybody is able to conduct.
You will notice that illusion eliminates. What’s the reason?

[zeroca]

To illustrate the fact that the pictures of both eyes are laid over each-other, is another test:
Take a little pipe (diameter 3-4 cm, length – 10-12 cm); look through it with one (right) eye; place your left palm before your eyes so that it touched farthest from eyes end of the pipe with its cubital part (consult the rough sketch below). Open/close the right eye several times (make sure that with your left eye you are watching your palm undamaged – without hole in it).
Open right eye (i.e. both eyes) finally.
You see a hole in your palm, i.e. you are looking through it, and when moving the palm nearer to left eye along the pipe, you see that hole penetrates the central part of palm.

[zeroca]

To explain the told above phenomenon isn’t hard: As I mentioned in my previous posts Flashing light reversal (posts #24, 25, 26), exact overlapping of images happens only in focal point (central vision) and all other points of scenario, i.e. all rest part of whole field of vision is doubling when looking at them with binocular vision (with both eyes), so contours of circles at crosses are coincided with color of background (squares), so the effect of illusion is the result of physiological doubling that takes place within the whole field of vision except for a small field of central vision. So that’s the reason of eliminating of illusion when narrowing the eyes (as narrowing of eyes covers peripheral vision and leaves functioning only central one).
When looking at the picture with monocular vision (with one eye open) illusion takes place because of shifting of eye slightly, so if you fix the vision with it, you’ll notice that illusion eliminates.
The truth, this illusion arises only when circles and background are contrasting.

[zeroca]

Here’s one more optical illusion:

The Ehrenstein illusion is an optical illusion studied by the German psychologist Walter Ehrenstein in which the sides of a square placed inside a pattern of concentric circles take an apparent curved shape.

[baudrunner]

If you try hard enough by staring at the center and forcing your mind to accept what you know to be true then the square will return to its proper shape. The reason it looks to be distorted is because of the proximity to the straight lines that the circular ones make, which spread out farther as they approach the corners. It is only a ho-hum and predictable optical illusion.

Here is a frighteningly real illusion. The lines are actually straight and keep their rigidity even while their contents are changing.

[zeroca]

I offer my own modification of Erhenstain illusion. You see that square appears distorted, but differently (Picture 1).

Let’s put one picture of Erhenstain illusion on another: you see that perceived picture of square depends on a background:

[zeroca]

See the modification of Hering illusion (animation). Parallel lines seem distorted but differently at different background.

[zeroca]

Here’s one more illusion. Let's call it zeroca's illusion. Both regular squares seem distorted.