Illusions By Linda Doan

The Hermann Square Do you see gray circles in the intersection of the squares? Look again, do those circles really exist?

The Hermann Square’s Explanation Explanation #1: PROXIMITY IMAGE The dark squares are so close together and the eyes are used to seeing things closed up. Because the square are slightly apart, the eyes make the image as if they are together. Explanation #2 Our eyes respond to a variety of light sources ranging from dark to light. Since there are more black than white, the eyes try to adjust to the dark level causing the white to look gray.

Explanation to the Hermann Square Taken Online “This is caused by a phenomona called "the centre surround analysis."This is due to a physiological mechanism called lateral inhibition. Your eye has two sets of receptors in the eye (called ganglions), one set in the centre and the other surrounding it. When the central one is stimulated the signal is sent straight though to the brain. But when the surrounding ones are stimulated, they also send a signal to the brain, but at the same time inhibit the central ones.Thus when looking at the grid, and focusing on one paticular point, the amount of inhibition varies depending on the quantity of "alternative" stimulation around that point. Thus the crossroads have black spots, due to the 4 adjacent squares. The amount of inhibition is enough for the brain to be into blotting out the crossroads with a grey spot. The other area's of the grid stay white, because the inhibition is not sufficient for the brain to black them out.It also works for coloured grids, with a similar effect, other than the spot changes colour depending on the 2 grid colours (eg blue spots in a green/yellow grid). This shows that it works for cone cells as well as rod cells.” From: Why does the Ilusions arise? “ illusions/page4.html” 2002.

Rotating Circles Stare into the red dot in the circle and slowly move towards the screen. What do you see? The rings on the outside are moving in different directions right? Are they really moving?

Rotating Circles’ Explanation The reason why you ‘re seeing this is because the eyes are used to seeing motions and to perceive things. Because you are staring at a certain angle and moving away the computer, the eye assume that it is moving. The rings seem rotate different directions because the shape of each ring appears to go different directions. In other words, the eye interpretes visual indication to assist in day to day living. In this case, the visual indication mislead one to perceive motion.

Two Shades of Green Look at the two shades of green. They appear to be different shades of green. Are they really?

Two Shades of Green’s Explanation Dithering A technique of creating a new colors where the colors are printed so close together that they mix to create a new color. Dithering is used primarily for color printing. If you look very closely at a magazine picture, you will see how the full-color pictures are actually made from thousands of small dots using this color dithering process The two shades of green that you were looking at were really just one shade of green. The reason why you see a darker green is because of the dark color next to it. The dark colors combine together to give you the dark shade of green. The same with the light shade. This technique is called dithering.

Tree Work of Art Look closely at the picture and tell me what you see? Is it a tree or heads of people?

Tree Work of Art’s Explanation Figure ground This is when you see different images when you take different objects on the painting as the background. For example: a picture of a vase. If you take the vase as the background, you will see two faces, while if you take the faces as the background you will see the vase. When you are just glancing at this picture, you might just see a tree. But if you look at it deeply and take the different object for the background, you might notice a difference. If you take the white as the background, you will see a tree. But if you take the trunk of the background as the background, you will see different heads.

A Bird In The Bush What is this sign saying? A BIRD IN THE BUSH? Look again.

A Bird In The Bush’s Explanation There are two thes. The reason you’re seeing that is because your brain assume things. All these years that you have been reading, there are rarely any sentence that includes two thes side by side. Your eyes read the sign and tends to skip the word that does not seem right.

Blind Spot Look at the X with your left eye closed. Move slowly towards or away from the screen. At a certain distance from the screen, you will notice the O to disappear. Why?

Blind Spot’s Explanation Although our eyesight seems complete in each eye, there is actually a large "hole" or blindspot created by the spot in the retina where the nerves exit the eye. Therefore, as you move back and forth, the O will be in the blind spot where you will not see the O.