Perceptual Constancies

Perceptual Constancies

Perceptual constancies allow us to perceive objects as unchanging even though there is a changing stimulus.

Size Constancy

With size constancy, our perceptions of the size of objects are relatively constant despite the fact that the size of objects on the retina vary greatly with distance.

This picture shows how our eyes perceive  the size of the wooden cross-braces to be the same since railroad tracks run parallel, when in the picture they are different sizes.

Brightness Constancy

Brightness constancy refers to our ability to see objects as continuing to have the same brightness even though light may change their immediate sensory properties.

In the picture above, the green pants of the person on the left look darker than the pants of the person on the right, and the grey shirt of the person on the left looks brighter than the shirt of the person on the right. This is all because the background on the left is much darker than the picture on the right.

Shape Constancy

Shape constancy helps us in perceiving the "real" shapes of objects regardless of their retinal projections. A familiar object keeps its perceived shape despite major changes in retinal stimulation due to changes in its orientation.

In this picture, all three panels are perceived to be the same shape regardless of their different drawn shape. Even the the shapes are drawn differently to give the shapes depth, we perceive them all to be the same shape.

Motion Perception

Motion Perception

In motion perception, motion is perceived when two different retinal pathways converge together allowing for the speed and direction of objects to be inferred

This video shows how motion is perceived and can be changed because of different laws.

This video shows how the aliens see a Charlie Chaplin film and how its motion is perceived through a series of images. 

Monocular Cues

Monocular Cues

Monocular cues are part of the depth-perception ability to sense the distance of an object; these cues are monocular because they can be sensed with just one eye.

Motion Parallax

In motion parallax, with perception through motion, objects that are closer seem to move faster than objects that are further away

    

The mountains in the background appear to be moving very slowly compared to the ground in the front.

Linear Perspective

In linear perspective, parallel lines seem to meet as they travel together to a distance.

http://education-portal.com/cimages/multimages/16/railroad_tracks.png

The railroad tracks appear to converge in the distance although they are actually parallel.

Binocular Cues

Binocular Cues

Binocular cues are depth cues, such as retinal disparity and convergence, that depend on the use of two eyes. 

The image above shows an example of retinal disparity, a type of binocular cue. Retinal disparity compares the images of an object seen from each of the eyeballs (for example, close your right eye and view the image from your left eye, and then do the opposite by closing your left eye and viewing the image from your right eye). You should see very different images/perspectives of the same object when you compare each of the images from each of your eyes. In the image above, the little house is visible from the perspective of the right eye but not the left.

Rules of Perceptual Organization

Rules of Perceptual Organization

Closure

Closure occurs when we create a complete, whole-object perception in our minds of an object that we see as incomplete.

Here, we perceive this set of black dots/splotches that are moving as a Dalmatian running. Why? This is because of closure. There isn't actually a dog there, but our minds will "connect the dots" of this image and turn these dots into what we see as a dog running.

Continuity

Continuity is the law that displays the concept of perceiving smooth, continuous patterns rather than discontinuous ones.

When we look at an X, we don't see two greater than and less than signs, we see two straight lines that cut across one another. Even though both patterns form the same shape, we perceive the lines because they are continuous.

Similarity

Similarity is when we group figures that are similar together, rather than dissimilar figures together.

  

In this image we see circles and squares. However, because of the perception law of similarity, we group the squares together and the circles together. This creates the perception of a cross created by squares in the center, outlined by the circles. This image will take precedence over all other perceptions, such as seeing 5 distinct horizontal or vertical lines, because of the law of similarity.

Proximity

Proximity occurs when we tend to group nearby figures together.

In the picture above, we are likely to perceive two groups of four black squares, instead of eight individual black squares. This is because the gap in between the two "pairs" of four squares makes us group the closest black squares together.

Figure-Ground Perception

Our first perceptual task is to perceive any figure as distinct from its surroundings, called the ground. Thus, figure-ground perception is the organization of the visual field into figures that stand out from their surroundings (the ground).

The image above can be perceived in two different ways. For example, if you perceive the black as the surrounding (ground), you will see a vase. However, if you perceive the white as the surrounding (ground), then you will see two faces.