Role of Top-Down Processing in Producing Vulnerability to Illusion.

Perceptual Constancy

our ability and need to perceive objects as unchanging even as changes may occur in distance, point of view, and illumination

Color Constancy

Perception that the color of an object remains the same even if lighting conditions change

Size Constancy

Tendency for the brain to perceive objects as the same apparent size regardless of their distance from us

Shape Constancy

Our viewing angle changes or an object rotates and we still perceive the object as staying the same shape

Lightness Constancy

Occurs when our perception of the whiteness, blackness, or grayness of objects remains constant no matter how much the illumination has changed

Binocular Cues

depth cues, such as retinal disparity, that depend on the use of two eyes

Retinal Disparity

a binocular cue for perceiving depth: by comparing images from the retinas in the two eyes, the brain computes distance - the greater the disparity between the two images, the closer the object

Convergence

When two eyes move inward (towards the nose) to see near objects and outward (away from the nose) to see faraway objects.  More ____ – closer the object

Monocular Cues

depth cues, such as interposition and linear perspective, available to either eye alone

Relative Size

If two objects are similar in size, we perceive the one that casts a smaller retinal image to be farther away.

Interposition

Objects that occlude (block) other objects tend to be perceived as closer

Relative Clarity

because light from distant objects passes through more light than closer objects, we perceive hazy.  objects to be farther away than those objects that appear sharp and clear.

Relative height

we perceive objects that are higher in our field of vision to be farther away than those that are lower.

Relative Motion

Objects closer to a fixation point move faster and in the opposing direction to those objects that are farther away from a fixation point, moving slower and in the same direction. 

Linear Perspective

Parallel lines, such as railroad tracks, appear to converge in the distance. The more the lines converge, the greater their perceived distance.

Light & Shadow

Nearby objects reflect more light into our eyes than more distant objects. Given two identical objects, the dimmer one appears to be farther away.

Texture Gradient

Indistinct (fine) texture signals an increasing distance.  Less detail shows closeness, finer and denser is further away