AP Psychology Unit 4: Sensation and Perception Key Terms

Sensation

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

Perception

the process of organizing and interpreting sensory information, enabling us to recognize meaningful objects and events

Bottom-up processing

analysis that begins with 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 drawings on our experiences and expectations

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

Psychophysics

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

Absolute threshold

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

Signal detection theory

a theory predicting how and when we detect the presence of a faint stimuli amid background stimulation (assumes there is no single absolute threshold)

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 (a just noticeable difference)

Weber’s law

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

Sensory adaptation

diminished sensitivity as a consequence of constant stimulation

Transduction

conversion of one form of energy into another

Wavelength

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

Hue

the dimension of color that is determined by wavelength of light

Intensity

the amount of energy in a light or sound wave, which we perceive as brightness or loudness, as determined by the wave’s amplitude

Pupil

the adjustable opening 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 inner surface of the eye, containing the receptor rods and cones plus layers of neurons that begin the processing of visual information

Accomodation

the process of 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; necessary for peripheral and twilight vision, when cones don’t respond

Cones

retina receptor cells that are concentrated near the center of the retina and that function in daylight or in well-lit conditions (detect fine details 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 (no receptor cells are located there)

Fovea

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

Feature detectors

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

Parallel processing

the processing of many aspects of a problem simultaneously

Young-Helmholtz trichromatic theory

the theory that the retina contains three different 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

Opponent-process theory

the theory that opposing retinal processes enable color vision

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 tiny bones (hammer, anvil, and stirrup) that concentrate the vibrations of the eardrum on the cochlea’s oval window

Cochlea

a coild, bony, fluid filled tube in the inner ear through which sound waves trigger nerve impulses

Inner ear

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

Place theory

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

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

Conduction hearing loss

hearing loss caused by damage to the mechanical system that conducts sound waves to the cochlea

Sensorineural hearing loss

hearing loss caused by damage to the cochlea’s receptor cells or to the auditory nerves

Cochlear implant

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

Kinethesis

the system of sensing the position and movement of individual body parts

Vestibular sense

the sense of body movement and position, including the sense of balance

Gate-control theory

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

Sensory interaction

the principle that one sense may influence another

Gestalt

an organized whole (emphasizes our tendency to integrate pieces of information into meaningful wholes)

Figure-ground

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 cues

depth cues, such as retinal disparity, that depend on the use of two eyes

Retinal disparity

a binocular cue for perceiving depth by comparing images from the retinas of two eyes, the brain computes distance (the greater the difference between the two images, the closer the object

Monocular cues

depth cues, such as interposition and 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 similar objects as having consistent color, even if changing illumination alters the wave-lengths reflected by the object

Perceptual adaptation

in vision, the ability to adjust to an artificially displaced or even inverted visual field

Perceptual set

a mental predisposition to perceive one thing and not another

Extrasensory psychology

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