Visual Illusions

Darwin Illusion- Visual illusion in which retinal impressions persist after the removal of a stimulus, believed to be caused by the continued activation of the visual system. For example, if you stare at the center of the image form at least ten seconds then look at a wall or blank surface, you will see the face of Charles Darwin hence the name the Darwin Illusion. Charles Darwin's face is what we refer to as an afterimage.















Cafe Illusion- The horizontal lines in this image appear to be sloping, but in reality they're parallel to one another. This is because it's easy to see the mortar line between two black tiles or two white tiles, it's much harder to see the mortar line between a white tile and a black one. Your brain fills in the gap by seeing it as part of either a white or black tile. This makes the tiles look wider at one end than at the other creating the illusion of a series of wedge-shaped tiles. This is what makes the lines appear to slant. 









Impossible Staircase(The Penrose Stairs)- The actual model is separated at the right stair, but you can't see the split, because your visual system assumes that it is seeing this model from a non-accidental point of view. This causes you to assume that the stairs are joined.

Perceptual Constancies

Size Constancy- Perceiving that objects have a constant size, even while our distance from them changes. For example, the left half of the picture is what we would normally see and you notice that the man in the back is fairly tall, but on the right half it shows just how big the man is in our minds eye. Size constancy is whats making the man appear to be bigger than how he really looks in our minds eye.


















Shape Constancy- We perceive the form of familiar objects as constant even while our retinal images of them change. For example, in the picture we see a quarter that is being rotated and at all points of the rotation we know that the quarter is a circle, but the shadow shows what the quarter really looks like throughout the rotation.















Brightness Constancy- We perceive an object as having a constant lightness even while its illumination varies. For example, in the picture both people have the same clothing on that are the same color. The reason it looks different is because of its surrounding. Our mind is trying to adapt to the difference in light.

Monocular Cues

Relative size- If we assume that two objects are similar in size, we perceive the one that casts a smaller retinal image as farther away. For example, the coke can on the left is smaller than the can on the right so we perceive it to be farther away.













Relative Clarity- Because light from distant objects passes through more atmosphere, we perceive hazy objects as farther away, than sharp, clear objects. For example, in the picture the far away mountains look hazy compared to the road that is right in front of you.
















Relative motion- As we move, objects that are stable may appear to move. The closer the object the faster it moves. For example, in the picture the red arrows show how fast the object is moving. Sp the mountain is moving very slow and the grass is moving very fast, because it is closer than the mountains.

















Interposition- If one object partially blocks our view of another, we perceive it as closer. For example, in the picture on the left the big rectangle is covering up part of the smaller rectangle so the big one appears to be closer. On the right it is the opposite so the smaller rectangle appears closer.
















Linear Perspective- Parallel lines appear to converge with distance. The more the lines converge, the greater their perceived distance. For example, either side of the road is parallel to each other and as you look further down the road you can see the road start to come to a point, because it is farther away.

Binocular Cue

Retinal Disparity- By comparing images from the two eyeballs, the brain computes the distance- the greater the disparity (difference) between the two images, the closer the object. This also shows that our left and right eye each see slightly different images from one another. An example is this picture where the left eye doesn't see the house and sees all the trees, and the right eye sees the house but not all of the second tree.

Convergence- The extent to which the eyes converge inward when looking at an object. The greater the inward strain, the closer the object. An example would be that when you read a book your eyes are pointed inward more than if you were trying to read a billboard that is far away.

Reversible Figures

This is a figure that can be seen from two different perspectives. A very famous example of this would be the duck-rabbit figure where both a rabbit and a duck can be seen depending on your perspective. Another example would be the face and liar picture where there is a face but it also spells out liar.

Phi Phenomenon

This is where there is an illusion of movement created when two or more adjacent lights blink on and off in quick succession. An example of this that everyone knows is the buffering wheel you see when watching videos.

Stroboscopic Motion

This is where your brain will perceive continuous movement in a rapid series of slightly varying images. An example of this would be any animated tv show like Spongebob or movie like The Incredibles.

Rules of Perceptual Organization

Closure- This is when we fill in the gaps to create a complete, whole object. An example would be the world wild life fund. It is a panda but we only see a panda due to closure












Continuity- When we perceive smooth, continuous patterns rather than discontinuous ones. An example would be this black and red "x" like figure. We perceive this as one continuous object, but really it is four separate line segments that meet at one point.










Similarity- Where we group together figures that are similar to one another. For example, we group this picture into columns of red and black circles. We don't see it as just a bunch of colored circles.









Proximity- Where we group nearby figures together. An example is that the squares on the left just look like a bunch of individual black squares, but when but close together on the right we group them together and see them form a cube.











Figure-ground perception- The organization of the visual field into objects (the figures) that stand out from their surroundings (the ground). For example, in the picture you either see a white cup, which is the figure and the black around it is the ground. You can also see two faces, which is the figure, and the white in between them is the ground.