Unit 3: Sensation and Perception

wavelength

the distance from the peak of one light or sound wave to the peak of the next.

hue

the dimension of color that is determined by the wavelength of light.

intensity

the amount of energy in a light wave or sound wave, which influences what we perceive as brightness or loudness.

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 colored muscle around the pupil and controls the size that the pupil can open.

lens

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

accommodation

the process by which the eye’s lens changes shape to focus near or far objects on the retina.

rods

retinal receptors that detect black, white, and gray, and are sensitive to movement. active in dark conditions.

cones

retinal receptors that are concentrated near the center of the retina and detect fine detail and color. active in light conditions.

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, so no receptor cells are present.

fovea

the central point in the retina around which the cones cluster.

young-helmholtz trichromatic theory

the retina contains three different color receptors, red, green, and blue. when stimulated in combination, they produce the perception of color.

opponent process theory

opposing retinal processes (red-green, yellow-blue, white-black) enable color vision.

feature detectors

nerve cells in the brain’s visual cortex that respond to features of stimulus such as shape, angle, and movement.

parallel processing

processes many aspects of a problem at once.

gestalt

an organized whole. gestalt psychologists emphasize our tendency to integrate pieces of information into a meaningful whole.

figure-ground

refers to the organization of the visual field into objects that stand out from their surroundings.

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.

retinal disparity

a binocular cue for perceiving depth. by comparing retinal images from the two eyes, the brain computes distance. the greater the disparity between the two images, the closer the object.

monocular cue

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

phi phenomenon

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

perceptual constancy

perceiving objects as unchanging 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 objects.

perceptual adaptation

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

audition

the sense or act of hearing.

frequency

the number of complete wavelengths that pass a point in a given time.

pitch

a tone’s experienced highness or lowness, depends on frequency.

middle ear

the chamber between the eardrum and cochlea containing three bones (hammer, anvil, stirrup) that concentrate the vibrations of the eardrum on the cochlea’s oval window.

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.

sensorineural hearing loss

caused by damage to the cochlea’s receptor cells or to the auditory nerves. the most common form of hearing loss.

conduction hearing loss

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

cochlea implant

a device for converting sounds into electrical signals and stimulating the auditory nerve through electrodes placed in the cochlea.

place theory

in hearing, the pitch we hear is linked with the place where the cochlea’s membrane is stimulated.

frequency theory

in hearing, the rate of nerve impulses traveling up the auditory nerve matches the frequency of a tone, thus enabling us to determine its pitch.

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 of organizing and interpreting sensory information

bottom-up processing

analysis that begins with 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, when we construct perceptions based on experience.

selective attention

the focusing of conscious awareness on a particular stimulus.

inattentional blindness

when we fail to see visible objects when our attention is directed elsewhere.

change blindness

when we fail to notice changes in the environment, a form of inattentional blindness.

transduction

the conversion of one form of energy into another. stimulus energy turns into neural impulses the brain can interpret.

psychophysics

the study of relationships between the physical characteristics of stimuli and our psychological experience of them.

absolute threshold

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

subliminal stimuli

stimuli below one’s absolute threshold for conscious awareness.

signal detection theory

predicts how and when we detect the presence of a faint stimulus amid background stimulation. assumes there is no single absolute threshold, detection depends on experience.

difference threshold

the minimum difference between two stimuli required for detection 50 percent of the time, experienced as a just noticeable difference.

priming

the activation of certain associations, thus predisposing one’s perception, memory, or response.

weber’s law

the principle that to be perceived as different, two stimuli must differ by a constant minimum percentage.

sensory adaptation

diminished sensitivity as a consequence of constant stimulation.

perceptual set

a mental predisposition to perceive one thing and not another.

extrasensory perception (ESP)

the controversial claim that perception can occur apart from sensory input. includes telepathy, clairvoyance, and precognition.

parapsychology

the study of paranormal phenomena, including ESP and psychokinesis.

gate-control theory

the spinal cord contains a neurological “gate” that blocks pain signals or allows them to pass onto 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.

olfaction

the sense of smell

kinesthesia

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

vestibular sense

the sense of body movement and position that enables our sense of balance.

sensory interaction

the idea that one sense may influence another.

embodied cognition

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