Unit 3: Sensation and Perception

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AP Psychology

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67 Terms


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


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

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

selective attention

the focusing of conscious awareness on a particular stimulus

inattentional blindness

failure to see visible objects when our attention is directed elsewhere

change blindness

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


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 brain can interpret


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% of the time

signal 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


below one's absolute threshold for conscious awareness

difference threshold

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


the activation, often unconsciously, 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 (rather than a constant amount)

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


the study of paranormal phenomena, including ESP and psychokinesis


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 gamma rays to the long pulses of radio transmission


the dimension of color that is determined by the wavelength of light; what we know as color names


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


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


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


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


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


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


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


retinal receptors that are concentrated near the center of the retina and that function in daylight or in well-lit conditions. 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


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

Young Helmholtz trichromatic (three-color) theory

the theory that the retina contains three different types of 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

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.

feature detectors

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

parallel processing

processing many aspects of a problem simultaneously; the brain's natural mode of information processing for many functions, including vision


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


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


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 (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

phi phenomenon

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

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 are having consistent color, even if changing illumination alters the wavelengths reflected by the object