Shape Constancy

Shape Constancy is when we perceive a form of a familiar object as having a constant shape, even when the image of it truly does change. An example would be an outlet. When looking at it from above, we see that it portrays a shape of a square more than anything. However, because we know the familiar object, we still perceive it as being rectangular.

Brightness Constancy

Brightness Constancy is how we perceive an object as having a constant lightness even when its illumination varies. We also perceive an object as having relative luminance, which means that the amount of light an object reflects is related to its surroundings. An example of this could be the two candles. One is directly in the light while the other is not, changing the colors of them. However, we still perceive them as being the exact same color.

Size Constancy

Size constancy is where we perceive objects as a constant size, even while our distance from them varies. Even though there may be a wide distance between you and the object being perceived, we still see that object of having the same constant size. An example of this is having two lotion bottles far apart. They have the same dimensions even though there is still much distance between them. We still have the ability to perceive that the furthest away bottle is the same size as the nearest.

 

Motion Perception

Motion perception illustrates the concept that our brain constructs our perceptions. Motion, for instance, is a mere perception of a series of still-images that are interpreted to show change in position. Animation uses such a technique in which still-images are flashed in quick, successive order to give the illusion of motion, here called stroboscopic movement. This idea is illustrated by the images below depicting a series of still-images in which a ball changes position. Should the images be shown in a rapid, successive order, the brain would perceive the changes in the ball’s position to be motion. 

Monocular Cue- Interposition

Interposition is a monocular cue that helps us to determine the relative depth of objects by considering which is closer. Specifically, if one object partially blocks the view of another, the object in front is perceived to be closer than the object it obscures. In the example below, the zebra figurine partially blocks the view of the cow behind it. As a result, our retinas correctly perceive the zebra to be closer to the eye than the cow. 

Monocular Cue- Relative Size

Monocular Cues aid in the depth perception of each eye separately when the disparity of an image is too slight to accurately determine depth. Relative size is one such indication of depth that assumes a smaller retinal image shows an object that is located farther away than those that appear larger. In the example below, is the passport booklet larger than a standard globe? If they were at the same distance, then the answer would be no; however, in this case, our retinas correctly assume that because the retinal image of the globe is smaller than that of the passport booklet, then the globe is farther away.  

Binocular Cue- Retinal Disparity

Binocular Cues are crucial tools in determining the extent of a human’s depth perception, that is, the ability to see both near and far. Because our eyes are separated by several inches, each of our retinas pick up different images, and the differences between them are called the retinal disparity. Because it is more difficult for the eyes to perceive a single image of objects closer to the retina, the closer the object, the greater the disparity. The pictures below illustrate the concept of retinal disparity; imagine that the top picture is the image received by the left eye and the bottom image is received by the right, and the same placement of the finger and camera are used in both images. Because the finger is very near to the retinas, it has a very high disparity, meaning that the image of the finger differs between the two pictures. However, because the globe is farther away, it has a lower disparity, and as a result the two images of the globe are relatively similar in placement.