Visual Illusion

Visual illusions or optical illusions are images that are visually perceived images that differ from objective reality.

http://www.opticaliillusions.com/Optical-Illusion-spinning-spirals.jpg

This image seems as if the edges are moving even though everything in the picture is perfectly still.

http://thecreatorsproject-images.vice.com/content-images/article/do-you-see-marilyn-monroe-or-albert-einstein-in-this-optical-illusion/89ae020999efcdcfad0d576a15c169ec.jpg?1xw:0.2587982832618xh;*,*&resize=1200:*

By focusing and unfocusing on the picture, one can see both Marilyn Monroe and Albert Einstein

http://brainden.com/images/old-couple.jpg

Looking at this picture, one can see an old couple but also a picture of a smaller couple.

Shape Constancy

Shape Constancy is when a perceived shape can appear the same when angle is changes.

In these pictures, the brain can tell that the frame is a rectangle even when turned at a 45°. Knowing that the frame is still a rectangle is called shape constancy.

Brightness Constancy

Brightness Constancy occurs when the brain perceives that a visual object has the same brightness under different conditions.

http://cpc.ehclients.com/images/uploads/whitehousenight.jpg
http://kgrafphoto.com/wp-content/uploads/2013/06/130608_WhiteHouse_Day.jpg

The White House is white but under the condition of night and day, the brain still perceives that the house is still white even when it is a different shade.

Size Constancy

Size Constancy is when the brain perceives objects as having constant size even as distance changes.

http://vignette1.wikia.nocookie.net/monoculardepthcues/images/2/26/Relative_Size_2.jpg/revision/latest?cb=20100323151151

In the first picture, it seems that the man in the blue is the same size as the man in the red. The second picture shows how size constancy can trick our brains into thinking that the two men were the same size.

Binocular Cues

Retinal Disparity
Retinal Disparity is when the brain compares images from each eye and computes the relative distance between them.

http://study.com/cimages/multimages/16/retinal_disparity_view.png

The difference between the left and right image is the brain's retinal disparity.



Convergence
Convergence is the way which the eyes converge inward when looking at an object

The closer the eyes converge, the closer the object is. In this picture, the object is very close to the very tired student that procrastinated his assignments.

Monocular Cues cont.

Interposition
Interposition is when one object partially blocks the view of another and the brain perceives it as a closer object.

http://webvision.med.utah.edu/gifswv/KallDepth2.GIF

The blue circle is overlapping the red circle however the brain perceives that the blue circle is closer.



Texture Gradient
Texture Gradient is a gradual change from course, distinct texture to fine, indistinct textures signals increasing distance.

https://c2.staticflickr.com/6/5051/5404019584_b2d753e569.jpg

This texture of the fence continues from right to left making it look like it is decreasing in size and farther away.



Linear Perspective
Linear Perspective occurs when parallel lines hat recede into the distance appear to get closer together or converge.

https://c1.staticflickr.com/1/43/108527640_ad8f94881c.jpg

The two railings of the train tracks are parallel but as they go farther into the distance, they look farther away.

Monocular Cues

Relative Size
Relative Size is when the brain assumes that if two objects are similar in size, the one that casts a smaller retinal image is farther away.

The iPhone's are the same size but since the white phone is farther away, the black phone seems bigger.

Relative Motion

Relative Motion is when the brain makes stable figures seem as if they were moving. This occurs when someone moves while staring at a certain object, the object seems to be moving backwards.

http://i.huffpost.com/gen/1487227/images/o-TEEN-LOOKING-OUT-CAR-WINDOW-facebook.jpg

Relative Height

Relative Height is when the brain perceives objects higher in our field of vision are perceived as farther away.

https://s-media-cache-ak0.pinimg.com/originals/dd/2d/a1/dd2da10501e4ce7bc15361ec5ec378e3.jpg

The house that is higher in the picture seems to be farther away from the ducks in the pond.

Relative Clarity

Relative Clarity is when light from distant objects passes through more atmosphere therefore they are perceived as hazy and farther away than sharp, clear object.

http://static.diary.ru/userdir/3/9/9/0/399040/19104639.jpg

In this picture, the flower is much clearer than the background due to the lack of light in the background and extra light on the flower.

Reversible Figures

Reversible Figures are images that can be seen as two different figures. These optical illusions exploit properties of visual interpretation between two or more image forms.

http://blog.joehuffman.org/wp-content/uploads/2013/01/woman.gif

This famous picture is an example of a reversible figure. One either sees an old lady or a young woman. The young woman has her head turned while the old lady seems to be looking down.

Phi Phenomenon

Phi Phenomenon can be defined as an optical illusion when viewing multiple still images in rapid succession, the viewer sees it as continuous motion.

https://upload.wikimedia.org/wikipedia/commons/6/6e/Lilac-Chaser.gif

In this example, multiple images of circles are shown and in succession. If starred at for a period of time, circles slowly disappear and only a green circle is left.

Perception of Movement

Perception of Movement or Stroboscopic Motion is when the brain perceives rapid images as motion or movement.

https://people.rit.edu/andpph/photofile-b/stroboscopy-basketball-1a.jpg

In this picture, the continuous movement of the basketball player seen here can be perceived as motion if shown individually.

Figure-Ground Perception

Figure-Ground Perception is when the brain can identify a figure from it's background.

http://pre10.deviantart.net/c51b/th/pre/i/2010/110/e/2/figure_ground_by_joshrother.jpg

This illusion can be seen as either a face of a lady or a mountain-side. What is seen depends on what is perceived as the background. 

Proximity

Proximity is when the brain groups nearby figures together.

http://blog.logis.org/wp-content/uploads/2012/10/people-meeting.jpg

This picture makes it seem like there are two different groups working together when they are in the same area.

Similarity

Similarity occurs when the brain groups figures together that are similar to each other.

http://ngscsports.com/wp-content/uploads/2015/09/Steelers-Ravens.jpg

This pictures represents similarity by grouping the Steelers in one group and the Ravens in another group due to the different color uniforms.

Continuity

Continuity is when the brain assumes and perceives smooth, continuous patterns rather than discontinuous ones.

https://maelstromjournal.files.wordpress.com/2013/12/stevemartin.jpg

In this picture, Steve Martin appears to have an arrow through his head due to the law of continuity.
It is actually just two pieces of an arrow attached to each side of his head.

Closure

The law of closure states that people often fill in gaps to create complete, whole objects.

http://cdn1.bloguin.com/wp-content/uploads/sites/94/2015/03/USA-Network.jpg

In this logo for the television channel USA Network, open lines between the "U" and the "A" help the brain fill in the gaps to perceive the letter "S", spelling out the word "USA".