Unit 2: Sensation and Perception

sensation

the process by which our sensory receptors and nervous system receive and represent stimulus energies from our environment

sensory receptors

sensory nerve endings that respond to stimuli

perception

the process by which our brain organizes and interprets sensory information, transforming it into meaningful objects and events

bottom-up processing

information processing that begins at the sensory receptors and works up to the brain's integration of sensory information

top-down processing

information processing guided by higher-level mental processes, as when we construct perceptions drawing on our experience and expectations

transduction

conversion of one form of energy into another. In sensation, the transforming of stimulus energies, such as sights, sounds, and smells, into neural impulses our brains can interpret.

psychophysics

the study of relationships between the physical characteristics of stimuli, such as their intensity, and our psychological experience of them

absolute threshold

the minimum stimulus energy needed to detect a particular stimulus 50 percent of the time

single detection theory

a theory predicting how and when we detect the presence of a faint stimulus (signal) amid background stimulation (noise). Assumes there is no single absolute threshold and that detection depends partly on a person's experience, expectations, motivation, and alertness.

subliminal

below one's absolute threshold for conscious awareness

priming

the activation, often unconsciously, of certain associations, thus predisposing one's perception, memory, or response

difference threshold

the minimum difference between two stimuli required for detection 50 percent of the time. We experience the difference threshold as a just noticeable difference (jnd).

Weber's law

the principle that, to be perceived as different, two stimuli must differ by a constant minimum percentage (rather than a constant amount)

sensory adaptation

diminished sensitivity as a consequence of constant stimulation

wavelength

the distance from the peak of one light or sound wave to the peak of the next. Electromagnetic wavelengths vary from the short blips of cosmic rays to the long pulses of radio transmission

hue

the dimension of color that is determined by the wavelength of light; what we know as the color names blue, green, and so forth

intensity

the amount of energy in alight wave or sound wave, which influences what we perceive as brightness or loudness. Intensity is determined by the wave's amplitude (height).

cornea

the eye's clear, protective outer layer, covering the pupil and iris

pupil

the adjustable opening in the center of the eye through which light enters

iris

a ring of muscle tissue that forms the colored portion of the eye around the pupil and controls the size of the pupil opening

lens

the transparent structure behind the pupil that changes shape to help focus images on the retina

retina

the light-sensitive back inner surface of the eye, containing the receptor rods and cones plus layers of neurons that begin the processing of visual information

accommodation

the process by which the eye's lens changes shape to focus the image of near or far objects on the retina

rods

retinal receptors that detect black, white, and gray, and are sensitive to movement; necessary for peripheral and twilight vision, when cones don't respond

cones

retinal receptors that are concentrated near the center of the retina and that function in daylight or in well-lit conditions. Cones detect fine detail and give rise to color sensations

optic nerve

the nerve that carries neural impulses from the eye to the brain

blind spot

the point at which the optic nerve leaves the eye, creating a "blind" spot because no receptor cells are located there

fovea

the central focal point in the retina, around which the eye's cones cluster

Young-Helmholtz trichromatic theory

the theory that the retina contains three different color receptors—one most sensitive to red, one to green, one to blue—which, when stimulated in combination, can produce the perception of any color.

opponent-process theory

the theory that opposing retinal processes (red-green, yellow-blue, white-black) enable color vision. For example, some cells are stimulated by green and inhibited by red; others are stimulated by red and inhibited by green

feature detectors

nerve cells in the brain's visual cortex that respond to specific features of the stimulus, such as shape, angle, or movement

audition

the sense or act of hearing

frequency

The number of complete waves that pass a given point in a certain amount of time

pitch

a tone's experienced highness or lowness; depends on frequency

cochlea

a coiled, bony, fluid-filled tube in the inner ear; sound waves traveling through the cochlear fluid trigger nerve impulses

inner ear

the innermost part of the ear, containing the cochlea, semicircular canals, and vestibular sacs

Sonsorineural hearing loss

The most common form of hearing loss, caused by damage to the cochlea's receptor cells/auditory nerve. also called nerve deafness

conduction hearing loss

less common form of hearing loss caused by damage to the mechanical system that conducts sound waves to the cochlea

cochlear implant device

for converting sounds into electrical signals and stimulating the auditory nerve through electrodes threaded into the cochlea.

place theory

in hearing, the theory that links the pitch we hear with the place where the cochlea's membrane is stimulated. (also called place coding.)

frequency theory

in hearing, the theory that the rate of nerve impulses traveling up the auditory nerve matches the frequency of a tone, thus enabling us to sense its pitch. (also called temporal coding).

gate-control theory

the theory that the spinal cord contains a neurological "gate" that blocks pain signals or allows them to pass on to the brain. The "gate" is opened by the activity of pain signals traveling up small nerve fibers and is closed by activity in larger fibers or by information coming from the brain.

gustation

our sense of taste

olfaction

our sense of smell

kinesthesis

our movement sense - our system for sensing the position and movement of individual body parts

vestibular sense

our balance sense - our sense of body movement and position that enables our sense of balance

sensory interaction

the principle that one sense may influence another, as when the smell of food influences its taste

embodied cognition

the influence of bodily sensations, gestures, and other states on cognitive preferences and judgements

selective attention

the focusing of conscious awareness on a particular stimulus

inattentional blindness

failing to see visible objects when our attention is directed elsewhere

change blindness

failing to notice changes in the environment; a form of inattentional blindness

perceptual set

a mental predisposition to perceive one thing and not another

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 into objects (the figures) that stand out from their surroundings (the ground).

grouping

the perceptual tendency to organize stimuli into coherent groups

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 cue

a depth cue, such as retinal disparity, that depends on the use of two eyes

convergence

a cue to nearby objects' distance, enabled by the brain combining retinal images.

retinal disparity

a binocular cue for perceiving depth. By comparing retinal images from the two eyes, the brain computes distance — the greater the disparity (difference) between the two images, the closer the object.

monocular cue

a depth cue, such as interposition or linear perspective, available to either eye alone

stroboscopic movement

an illusion of continuous movement (as in a motion picture) experienced when viewing a rapid series of slightly varying still images.

phi phenomenon

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

autokinetic effect

the illusory movement of a still spot of light in a dark room.

perceptual constancy

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

color constancy

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

perceptual adaptation

the ability to adjust to changed sensory input, including an artificially displaced or even inverted visual field