Sensation and Perception

SENSATION - receiving information from the environment or from the sensory organs

PERCEPTION - interpretation of the neural impulses or sensations

OBJECTIVE REALITY- that which really exists

SUBJECTIVE REALITY - that which we perceive as existing

Attention:

Automatic - attention without awareness; inflexible, economic, uncontrollable, parallel, occurs through practice, fast (habitual responding)

Attentional - intentional processing; aware, controlled, flexible, serial, slower; selective

Attention Getting Devices:

External attention getting devices -

intensity and size

contrast - unexpected stimuli (orienting response)

repetition

movement we naturally respond to movement (midbrain)

Internal attention getting devices

motives and emotions needs, interests

set or expectancy past experience tunes us primed

Organization in Perception

The GESTALT school of psychology theorized that we perceive information in our environments in organized ways.

the whole is greater than the sum of its parts

Principles of perceptual organization:

Figure-Ground we see an object as standing out in relation to a general background; the figure has form and the ground is formless

Grouping how we structure our perceptual field; the properties of the whole affect the way in which the parts are perceived. We perceive ordered relationships.

Proximity nearness; items close together in time or space tend to be perceived as belonging together;

Similarity items similar in respect to some feature tend to be grouped

Common direction or Good continuation implementation of a rule to infer a pattern;

Contour a marked difference in the color or brightness of the background

Closure completing an incomplete percept - filling in the gaps

Perceptual Constancy Optical images of objects change continuously and yet our perception of these objects does not

Size Constancy we perceive an object as being the same size over a wide range of distances

Shape Constancy perceiving a shape as constant regardless of the angle of orientation

Brightness constancy regardless of the light conditions, we perceive colors as the same

Depth Perception we translate 2 dimensional cues into 3 dimensional forms and perceive depth

Monocular Cues one-eyed cues

linear perspective - relative size - far objects appear smaller; convergence of parallel lines; elevation of object's height in a horizontal plane

clarity the more clearly we see an object the closer it appears to be

shadows light coming from above gives either the impression of depth or height

superposition (interposition) when one object partially blocks another , we perceive the object doing the blocking as closer

texture gradients texture varies in density as it gets farther away, gives the impression of slope and depth

motion parallax - near objects move in a direction opposite to your movement and far objects move in the same direction

Accomodation thickness of the lens automatically adjusts to distances (nearsightness - lens does not adjust to far objects - lens doesn't thin)

Binocular cues two eyed cues;

Retinal disparity refers to the images falling onto the two eyes; the fovea - the most sensitive surface of the eye

Convergence a kinesthetic cue from the muscles that turn and point the eye.

Perception of movement

Our eyes are constantly in motion; we have large sweeping movements with our eyes called SACCADES and small tremor type movement called NYSTAGMUS

Apparent motion (not actual)

Stroboscopic Movement movement is experienced when the object appears to undergo a change in its location

Autokinetic effect (Phi Phenomenon) stationary point of light in a completely darkened area will appear to move when we fixate on it

Induced Movement a stationary form will appear to move when its frame of reference moves

movement in a stationary pattern the waterfall effect, op art

Real Movement

Speed - Our perception of speed depends on three factors: the background, the size of the moving object; and velocity.

Background - complexity increases the perception of movement

Size - smaller objects appear to be moving faster than larger objects

Velocity- actual velocity is difficult to judge; have limits

Color Vision

Cones - color

Rods - night vision

Three types of cones: short wavelength (blue); medium wavelength (green); long wavelength (red)

Hue - determined by wavelength

Brightness - determined by intensity

Saturation - equals purity (light of only one wavelength)

Color mixing adding wavelengths of light

Paint mixing (subtracting color)

Negative afterimages (Opponent Process theory)

Color blindness

Dichromacy (2 colors)

Protanopia (lack red)

Deuteranopia (lack green)

Tritanopia (lack yellow-blue )

Monochromacy no cones