PSY2012 Ch.4 - Sensation and Perception

sensation

process of receiving stimulus energies from the external environment

perception

process of organizing and interpreting sensory information to give it meaning

bottom-up processing

begins with sensory receptors registering environmental information and sending it to the brain for analysis and interpretation; “perception directs cognition”

top-down processing

processing of perceptual information that starts out with cognitive processing at the higher levels of the brain; “perception is constructed by cognition”

psychophysics

study of the links between the physical properties of stimuli and a person’s experience of them

absolute threshold

minimum amount of stimulus energy that a person can detect; the point at which stimuli is detected 50% of the time

subliminal perception

detection of information below the level of conscious awareness

difference threshold

smallest difference in stimulation required to discriminate one stimulus from another 50% of the time

Weber’s law

two stimuli must differ by a constant minimum percentage to be perceived as different

signal detection theory

detection of stimuli depends on a variety of factors besides the physical intensity of the stimulus and the sensory abilities of the observer

information acquisition

one component of signal detection theory; “what information is present?”

criterion

one component of signal detection theory; “is the signal for detection present?”

perceptual set

preexisting expectations/readiness to perceive a stimulus in a certain way

trichromatic theory

color perception is produced by 3 types of receptors that are particularly sensitive to different, but overlapping ranges of wavelengths

opponent-process theory

cells in the visual system respond to red-green and blue-yellow colors; evidence found in afterimages

gestalt

people tend to organize visual elements into “unified wholes” when certain principles are applied; the whole is different from the sum of its parts

gestalt theory

1. objects will be perceived in their simplest form
2. humans naturally follow lines or curves
3. the mind will attempt to fill in detail that isn’t actually there

continuation

gestalt principle which states the eye is compelled to move through one object and continue to another

closure

gestalt principle which occurs when an element is incomplete or a space is not totally enclosed; the viewer will subconsciously fill in the missing information

similarity

gestalt principle

proximity

gestalt principle which occurs when elements are placed close to each other; helps to portray a relationship between the separate parts

symmetry

gestalt principle which states elements that are symmetrical to each other tend to be perceived as a unified group

figure & ground

gestalt principle which states the eye differentiates an object from its surrounding area

depth perception

our ability to perceive objects three-dimensionally

binocular cues

depth cues based on the combination of the images of the left and right eyes

monocular cues

depth cues that are available from the image in either eye

familiar size

cue to the depth & distance of objects based on what we have learned from experience about the standard sizes of objects

height in the field of view

all other things being equal, objects positioned higher in a picture are seen as farther away

linear perspective

objects that are farther away take up less space on the retina; parallel lines appear to converge

overlap

an object that partially conceals or overlaps another object is perceived as closer

shading

involves changes in perception due to the position of the light and position of the viewer

texture gradient

texture becomes denser and finer the farther away it is from the viewer, creating depth

apparent movement

occurs when an object is stationary, but we perceive it as moving

perceptual constancy

the recognition that objects are constant and unchanging even though sensory input about them is changing

size constancy

the recognition that an object remains the same size even though the retinal image of the object changes

shape constancy

the recognition that an object remains the same shape even though its orientation to us changes

brightness constancy

the recognition that an object remains the same degree of brightness even though different amounts of light fall on it

visual illusions

occur when there is a discrepancy between reality and the perceptual representation of it

pain

the sensation that warns us that damage is occurring to our bodies

gate control theory of pain

states that the spinal column contains a neural gate that can be opened (allowing the perception of pain) or closed (blocking the perception of pain)

olfactory epithelium

sheet of receptor cells for smell that lines the roof of our nasal cavity

major histocompatibility complex

mates with differing genes from us generate the healthiest offspring because they contribute broader immune systems to the gene pool