Tuesday, February 25, 2014

Test your Brain with these Top 10 Visual Illusions_Part 2/2

Check your answers and learn about what was going on in your brain while you expe­ri­enced each of these illusions:

1. Can you put the fish in the fishbowl?
Did you see a fish of a dif­fer­ent color in the bowl? You have just expe­ri­enced an after­im­age.
In the retina of your eyes, there are three types of color recep­tors (cones) that are most sen­si­tive to either red, blue or green. When you stare at a par­tic­u­lar color for too long, these recep­tors get “fatigued.” When you then look at a dif­fer­ent back­ground, the recep­tors that are tired do not work as well. There­fore, the infor­ma­tion from all of the dif­fer­ent color recep­tors is not in bal­ance. This will cre­ate the color “afterimages.”

2. Bezold effect
The smaller squares inside the blue and yel­low squares are all the same color. They seem dif­fer­ent (magenta and orange) because a color is per­ceived dif­fer­ently depend­ing on its rela­tion to adja­cent col­ors (here blue or yel­low depend­ing on the outer square).
3. Café Wall Illusion
The hor­i­zon­tal lines are straight, even though they do not seem straight.  In this illu­sion, the ver­ti­cal zigzag pat­terns dis­rupt our hor­i­zon­tal perception.

4. Illu­sory Motion
The cir­cles do appear to be mov­ing even though they are sta­tic. This is due to the cog­ni­tive effects of inter­act­ing color con­trasts and shape position.

5. How many legs does this ele­phant have?
Tricky, isn’t it?! This pic­ture is an impos­si­ble pic­ture that also con­tains some sub­jec­tive con­tours, such as the Kanizsa Tri­an­gle below: A white tri­an­gle (point­ing down) can be seen in this fig­ure even though no tri­an­gle is actu­ally drawn. This effect is known as a sub­jec­tive or illu­sory con­tour. The con­tour of the tri­an­gle is cre­ated by the shapes around it.


6. The Mueller-Lyer Illusion
The two hor­i­zon­tal lines are of the same length, even though the one at the bot­tom seems longer.
As you know, the visual angle gets smaller with dis­tance, so the brain auto­mat­i­cally per­ceives objects at far­ther dis­tances to be big­ger.
In gen­eral, lines that have inward flaps, such as cor­ner of a build­ing, are rel­a­tively the near­est points of the over­all object. Sim­i­larly, lines with out­ward flaps are found at the longer dis­tance, as the far­thest cor­ner of a room.
So in the Mueller-Lyer illu­sion, the brain per­ceives the line with out­ward flaps to be at a far­ther point as com­pared to the line with inward flaps. Con­se­quently, the brain per­ceives the line with out­ward flaps to be longer.

7. Her­mann grid illusion
There are not gray dots in this grid. How­ever “ghost­like” gray blobs are per­ceived at the inter­sec­tions of the white lines. The gray dots dis­ap­pear when look­ing directly at an inter­sec­tion.
This illu­sion can be explained by a neural process hap­pen­ing in the visual sys­tem called lat­eral inhi­bi­tion (the capac­ity of an active neu­ron to reduce the activ­ity of its neighbors).

8. The Ebbing­haus Illusion
The two orange cir­cles are exactly the same size, even though the one on the left seems smaller.
This size dis­tor­tion may be caused by the size of the sur­round­ing cir­cles or by their dis­tance to the cen­ter circle.

9. Does Lincoln’s face look nor­mal?It seems nor­mal but now, look at it upright: Lincoln’s eyes do not look quite right!

Some neu­rons in the brain seem spe­cial­ized in pro­cess­ing faces. Faces are usu­ally seen upright. When pre­sented upside down, the brain no longer rec­og­nizes a pic­ture of a face as a face but rather as an object. Neu­rons pro­cess­ing objects are dif­fer­ent from those pro­cess­ing faces and not as spe­cial­ized. As a con­se­quence these neu­rons do not respond to face dis­tor­tions as well. This explains why we miss the weird eyes when the face is inverted.
10. Can you see a baby?Another great exam­ple of an illu­sory con­tour! The baby’s head is on the left, the baby’s feet are against the trunk of the tree on the right.

Article retrieved from: http://sharpbrains.com/blog/2010/10/27/test-your-brain-with-these-top-10-visual-illusions/


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