Visual Illusions

Visual Illusions- A visual perception that represents what is perceived in a way different from the way it is in reality.

Horizontal- Vertical Illusion: the tendency for observers to overestimate the length of a vertical line relative to a horizontal line of the same length. 

Ex.-  The two lines below are the same length, even though the vertical one seems longer.

http://static.newworldencyclopedia.org/thumb/7/7d/Horizontal-Vertical.jpg/225px-Horizontal-Vertical.jpg

Depth, Reversibility, and Figure Completion: When you look at the top figure, your visual system will organize the elements into a box. The box will reverse, as in the Necker Cube illusion. The elements in the bottom figure have terminations and do not readily group into a box figure that shows reversals.

http://dragon.uml.edu/psych/box_1.gif

Blind Spot: There is a certain spot on the optic nerve that does not have any receptor cells (the area where the optic nerve leaves the eye), and, as a result, can't receive information. 

https://onionesquereality.files.wordpress.com/2009/07/illustration-blind-spot.gif

Ex.- If you have a paper like the one below, you focus on the cross and move the paper away from you you will eventually reach a point where you can no longer see the dot.

http://img13.deviantart.net/487b/i/2015/089/8/c/can_you_find_your_blind_spot__by_eepawstep20-d8npsvs.jpg

Rules of Perceptual Organizaton

Closer:
Definition- This is the idea that the mind feels the need to complete an object it sees whether it is completed or not.
Example: Your mind makes it a circle or square without it actually being there.

http://www.ashpfoundation.org/transformational/law-of-closure.png

Continuity:
Definition-  It is the principal that states "whatever succeeds for the finite, also succeeds for the infinite"
Example: Your mind makes the conclusion that the lines go on forever even though they end.

https://blogtmssl-templatemonster.netdna-ssl.com/wp-content/uploads/2012/04/cross.jpg?37c8fc

Similarity:
Definition- Your brain takes a bunch of un-whole mixed up things and makes them whole and make sense.
Example- If you hear a bunch of different music playing you can still pick out each song even though there was tons of different words and notes to go along with it.

http://study.com/cimages/multimages/16/Ascii_smiley.jpg

Proximity:

Definition- When we see objects near each other we assume they have something to do together even if they don't. 

Example-

http://study.com/cimages/multimages/16/proximity_circles.jpg

Figure-ground Perception:

Definition- We tend to speate things from figure or object and ground or background.
Example- You either see a man playing a saxophone or a woman's face.

http://www.loyno.edu/~zemmels/A201/lecture/visual_theory/gestaltprinc.html

Perceptual Constancies - Sarah Lehman Pd. 3

Perceptual Constancies 

Size constancy- When an object is within a certain range, peoples perception of the size of that object will not change, regardless of  changes in distance, or "video size change to the retina."

Example- If you are only within a few feet from a dog or a cat, that animal can go back and forth a few feet, and they will still look generally the same size. 

https://upload.wikimedia.org/wikipedia/commons/2/24/Shape_constancy.gif

These doors are technically different distances away, yet that does not distort our perception of their size, as they all look the same size, 

Brightness Constancy- A visual object, even after being lit up in two entirely different conditions, say day and night, will appear to us as having the same brightness. 

Example- If you take a white paper plate in a brightly lit room, and then take it and put it into a dimly lit room, that plate will still appear to be the same color, with the same brightness

http://www.kevinconnery.com/imaging/samples/color_constancy_neutral.gif

As the shade of the outer boxes change, the apparent brightness and shade of the inner boxes still appears unchanged. 


Shape constancy- Even is the shape of an objects retinal image appears different, our perception of that object will remain the same. 

Example- As we see a door open and close, the rectangular shape may appear to get distorted, but we still perceive it as a rectangle.

http://psychology252.blogspot.com/2014/11/perception-laws-size-constancy-is.html

Both cubes are perceived to be the same shape, even though the retinal image of the second one is not exactly a cube. 

Depth Perception- Natalie Rhodes Pd 3

Monocular Cues- Depth cues such as interposition, relative size, and linear perspective available to each eye alone.

• Relative Size- If we assume two objects are similar in size we perceive the one that casts the smaller retinal image as farther away.

     Ex.- Relative size is used in paintings to add depth. Certain objects are depicted smaller than others to make them seem further away. Such as in the image below.

http://psych.hanover.edu/Krantz/art/scolls.jpg

• Relative Height- Objects higher in our field of vision are perceived as farther away; causes the illusion that taller objects are longer than shorter objects.

      Ex.- If you look at a landscape picture the objects in the foreground (such a a tree in this case), may seem to be the same size or even bigger than objects that are further away such as mountains. However, we know that mountains are much larger.

http://www.hdwallpaperscool.com/wp-content/uploads/2013/11/nature-landscape-beautiful-photos-best-desktop-landscape-hd-wallpapers-widescreen.jpg

• Relative Motion- As we move, objects that are stationary appear to move; the closer the object, the faster it appears to move.

      Ex.- If you go running you may think you are going fairly fast because objects near you are whizzing by, however if you look into the distance, objects that are further from you will not seem to be moving as fast.

http://www.daviddarling.info/images2/ship_moving_relative_to_jetty_1.jpg

• Interposition-If one object partially blocks the view of another, we perceive it as closer.

      Ex.- Placing one card on another (as shown below), and one card will seem further behind the other.

http://wps.prenhall.com/wps/media/objects/1029/1054447/images/3_31.gif

• Linear Perspective- Parallel lines seem to converge with distance; the greater the convergence, the greater the distance perceived.

      Ex.- Railroad tracks

http://azfoo.net/places/yucca/trip/13_Tracks.jpg

Binocular Cues- Visual information taken in by two eyes that enable us a sense of depth perception. 

• Retinal Disparity-The way that your left eye and your right eye view slightly different images. 

      Ex.- If you place your finger over an object fairly far away and close each ye one at a time the picture will be slightly different.

http://study.com/cimages/multimages/16/retinal_disparity.gif

• Convergence- The extent to which the eyes converge inward when looking at an object; the greater the inward strain, the closer the object.

      Ex.- When at the doctor's you may have been told to follow  pencil with your eyes. As you look at the tip of the pencil your eyes converge.

http://tonks.disted.camosun.bc.ca/courses/psyc110/percep/converg.gif

Period 9 Maher

Reversible Figures

Definition: Optical illusion images which exploit graphical similarities and other properties of visual system interpretation between two or more distinct image forms. This could cause one person to see an image one way, and cause someone else to see the same image another way. 

Example: The following image could be interpreted in two different ways. Do you see the old woman or the young girl first?

http://open-mind.net/epubs/bridging-the-objective-subjective-divide-towards-a-meta-perspective-of-science-and-experience/OEBPS/images/figure5.jpg

Period 9 Maher

Phi Phenomenon

Definition; The optical illusion of perceiving a series of still images, when viewed in rapid succession, as continuous motion. 

Example: A flip book made out of post-it notes can give the illusion of movement, when in reality they are just multiple still frames being played quickly after each other. 

This picture should show how it seems as if the man is flipping, when it is really just many still pictures side by side.

http://workflow.arts.ac.uk/artefact/file/download.php?file=754660&view=93658

Period 9 Maher

Perception of Movement (stroboscopic motion)

definition: the process of inferring the speed and direction of objects based on visual input at periodic intervals.

example: When you are in the car, you can tell how far away something is to you based on how long it takes for it to pass. A mailbox would pass a lot quicker than say the moon would.

This picture shows how when the passenger focuses on a single point, he can tell how fast he is going and/or how far away something is.

https://s-media-cache-ak0.pinimg.com/originals/d8/ef/0c/d8ef0c5a00c2659654a679623a36f656.jpg