Unit 2a: Perception

Sensation

The process by which you detect physical energy from your environment and encode it as neural signals. 

Perception

How we select, organize, and interpret our sensations.

Selective Attention

the focusing of conscious awareness on a particular stimulus.  With hearing, it’s known as the cocktail party effect.

Inattentional Blindness

failing to see visible objects when our attention is directed elsewhere.

Change Blindness

failing to notice changes in the environment.  Ex. The bearded man not noticing that the man giving directions was replaced by someone else after the board passed by

Perceptual Adaptation

in vision, the ability to adjust to an artificially displaced or even inverted visual field.  This is usually done with distorting lenses.  When the lenses are removed, it takes some time for perception to return to “normal”.

Perceptual Set

a mental predisposition to perceive one thing and not another.

Schema

Organized bodies of information that are stored in memory which can bias the way new information is interpreted, stored, and recalled.

Context Effects

describes the influence of environmental factors on one's perception of a stimulus.

Gestalt

an organized whole.  Gestalt psychologists emphasized our tendency to integrate pieces of information into meaningful wholes.

Figure-Ground

the organization of the visual field and sound into objects (the figures) that stand out from their surroundings (the ground). 

Grouping

the perceptual tendency to organize stimuli into coherent groups.

Proximity

We group nearby figures together

Similarity

We group similar figures together

Continuity

We perceive smooth, continuous patterns rather than discontinuous ones. 

Connectedness

Because they are uniform and linked, we perceive each set of two dots and the line between them as a single unit.  

Closure

We fill gaps to create a complete, whole object

Depth Perception

the ability to see objects in three dimensions although the images that strike the retina are two-dimensional; allows us to judge distance.

Visual Cliff

a laboratory device for testing depth perception in infants and young animals

Binocular Cues

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

Binocular Cues: 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 (difference) between the two images, the closer the object.

Binocular Cues: Convergence

a neuromuscular cue in which our two eyes move inward the closer the object gets to our face.

Monocular Cues

depth cues that depend on the use of one eye

Relative Height

we perceive objects higher in our field of vision as farther away.

Relative Size

if we assume two objects are similar in size, most people perceive the one that casts the smaller retinal image as farther away.

Interposition

if one object partially blocks our view of another, we perceive it as closer.

Linear Perspective

parallel lines, such as railroad tracks, appear to converge with distance.  The more they converge, the greater their perceived distance.

Relative Motion

As we move, objects that are actually stable may appear to move.

Light and Shadow

nearby objects reflect more light to our eyes. Thus, given two identical objects, the dimmer one seems farther away.  Shading, too, produces a sense of depth consistent with our assumption that light comes from above.

Phi Phenomenon

an illusion of movement created when two or more adjacent lights blink on and off in quick succession, like Christmas lights.

Autokinetic Effect

a visual illusion that occurs when a stationary point of light appears to move in a dark environment.

Stroboscopic Effect

a visual illusion that occurs when an object appears to move slower than it really does.

Perceptual Constancy

perceiving objects as unchanging (having consistent shapes, size, lightness, and color) even as illumination and retinal images change.

Size Constancy

perceiving familiar objects as having consistent size, even if changing surroundings makes them appear to change size. Ex. Moon illusion, Ponzo illusion, Ebbinghaus illusion

Shape Constancy

perceiving familiar objects as having a different shape if they project a different angle on our retina. Ex. A door that is slightly open doesn’t look the same when it is closed, but we know it is.

Color Constancy

perceiving familiar objects as having consistent color, even if changing illumination alters the wavelengths reflected by the object.