A Binocular Cue

Binocular cues are vital when trying to judge the distance of nearby objects.  A binocular cue is a depth cue, such as retinal disparity and convergence that depend on the use of two eyes. Retinal disparity is relatively simple.  Since our eyes are about 2.5 inches apart, each receives slightly different images of the world.  The closer an object is viewed to your eyes, the greater the disparity.  Likewise the further an object is viewed, the less difference there is between the images.  This example can be seen at two of the picture viewed here on the left and right.  Although both eyes are viewing the same image, they are viewing the image from slightly different vantage points creating slight differences.

Also, convergence is a binocular cue for perceiving depth.  It is caused by the greater inward turn your eyes do when they view a near object.  The brain has to do computations to focus in on what you are trying to see.  The greater the inward strain, the closer the object.

Figure-Ground Perception

The figure-ground system gives people a good understanding of how we perceive things. In a figure-ground system, we perceive an object, called the figure, as distinct against its surroundings, called the ground.  For example, look at the picture in this post. When someone looks at this picture, they will perceive that it spells out the name Jesus.  In this case the figure is actually the white colored shapes.  If someone tries to stare at those shapes by themselves, they will come to the conclusion that is nothing but gibberish.  However, when they perceive the figures against the dark green ground, they then realize that it spells out the name Jesus.  This is just one good illustration of how the figure-ground relationship works.

Shape constancy

 Shape constancy is when an object whose shape cannot change seem to change shape when the angle of our view is altered. Because of this we perceive an objects shape as constant even though its shape is changing in our retinas. An example is the book below where in the first picture the book is a rectangle and then when rotated it appears as a trapezoid although we still perceive it as a rectangle.

Brightness Constancy

Brightness constancy is when we perceive colors to be darker or lighter than they actually are based on the relative luminance. Relative luminance is the amount of light an object reflects relative to its surroundings. For example in the two pictures below the girls have the same skin tone, but the one on the left appears to have a lighter skin tone than the one on the right. Since the girl on the left is surrounded by grey it appears as if her skin color is lighter than the girl surrounded by white.

Size Constancy

Size constancy is when we instantly and unconsciously infer an object's size given its perceived distance and the size of its image on our retinas. This is shown in the picture below where the man in the background is farther away and appears larger than he actually is in the photo. Our brains are told that the man in the background is farther away therefore we perceive it as larger when in reality its real size compared to the man in the front is smaller.

Proximity

When perceiving objects, we often group nearby figures together.  Conversely, we see figures which are spaced apart from each other as entirely separate from one another. Consider the following example:

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When someone perceives this example, they could perceive it in many ways. The mostly likely way to perceive this is 3 sets of 2 lines.  This happens because the lines are spaced close to each other, so many people begin to group these lines together in their mind.  Someone, could also perceive 6 separate lines, however this is much less likely to occur due to the proximity of each of the lines with respect to one another.

Motion Perception

The brain perceives continuous movement in a rapid series of slightly varying images (stoboscopic movement), and the motion is constructed in our heads.  Another illusion of movement is created by the phi phenomenon.  This is when two or more stationary lights blink on and off in succession, and we perceive the light to be moving from one point to the next.  An example is the loading symbol.  It appears to be moving in a circle but the small rectangles are lighting up one right after another.

Monocular Cues 2

Another monocular cue we use is relative size.  We use relative size to perceive depth and placement of things in space.  The larger the image, the closer it is perceived to be. If an object grows it is perceived to be getting closer. Conversely, if it shrinks it appears to be getting further away.  This can be seen in the picture.  We perceive the creepy cow as being closer because it is bigger in comparison to the zebra. 

Monocular Cues

Monocular Cues are cues we use to judge depth that are processed by just one eye. Monocular cues are mainly used for depth perception An example is linear perception, where parallel lines seem to go towards each other as they move away from the viewer.  This is commonly used by artists to give their pieces depth and a realistic look.  We were taught linear perspective in art class when we were doing a realistic drawing unit.  Using linear perspective in art requires vanishing points

and straight lines.  This is a picture of when I first learned perspective drawing when I was 5 and I tried to make my drawings more realistic. 

Similarity

Similarity is when we group together figures that are similar to each other. An example of this would be when viewing this image below, we would view this as three horizontal rows of pasta due to the similarity in color, rather then one vertical column with a mix of colors.

Continuity

Continuity is when we perceive smooth, continuous patterns rather than discontinuous ones. An example of continuity can be shown through this image below. When looking at this image,  you would perceive the apples to be in one diagonal line. Continuity explains how we view this as one line rather than, in this case, two "V-shapes".

Closure

Closure is when we fill in gaps to create a complete, whole object. An example of this would be the famous "USA" television network. We can see the "U" and "A" that are present and our mind fills in the gap of the "S" to create the whole object.