Sensation and Perception Vocabulary

Sensation

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

Absolute threshold

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

Difference threshold

the minimum difference between two stimuli required for detection 60 percent of the time

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

Cornea

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

Accommodation

(1) in sensation and perception, the process by which the eye's lens changes shape to focus images of near or far objects on the retina; (2) in developmental psychology, adapting our current schemas to incorporate new information

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

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

Figure-ground

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

Fovea

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

Feature detectors

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

Trichromatic theory

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

Afterimage

a visual sensation that persists after the original stimulus has been removed

Opponent-process theory

the theory that opposing retinal processes (red-green; blue-yellow; 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

Audition

the sense or act of hearing

Eardrum (tympanic membrane)

a thin, cone-shaped membrane that separates the outer ear from the middle ear

Cochlea

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

Place theory (place coding)

in hearing, the theory that links the pitch we hear with the place where the cochlea's membrane is stimulated

Frequency theory (temporal coding)

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

Conduction deafness

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

Nerve deafness (sensorineural hearing loss)

the most common form of hearing loss caused by damage to the cochlea's receptor cells to the auditory nerve

Olfaction

our sense of smell

Taste buds

the sensory organs for taste, which allow us to perceive flavors

Gate-control theory of pain

the theory that the spinal cord contains a neurological 'gate' that blocks pain signals or allows them to pass on to the brain

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

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

Signal detection theory

a theory predicting how and when we detect the presence of a faint stimulus [signal] amid background stimulation [noise]

Inattention blindness

failing to see visible objects when our attention is directed elsewhere

Gestalt

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

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

Wavelength

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

Transduction

Conversion of one form of energy into another; in sensations, the transforming of physical energy, such as sights, sounds, and smells, into neural impulses the brain can interpret

Visual cliff

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

Psychophysics

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

Perception

the process by which our brain organizes and interprets sensory information, enabling us to recognize objects and events as meaningful

Selective attention

focusing conscious awareness on a particular stimulus

Perceptual set

a mental predisposition to perceive one thing and not another

Bottom-up processing

information processing 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, as when we construct perceptions drawing on our experience and expectations

Perceptual constancy

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

Binocular cues

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

Monocular cues

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

Retinal disparity

a binocular cue for perceiving depth; by comparing retinal images from the two eyes, the brain computes distance

Phi phenomenon

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

Parapsychology

the study of paranormal phenomena, including ESP and psychokinesis