Sensation and Perception

Absolute Threshold

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

Bottom-Up Processing

Definition: Analysis that begins with the sensory receptors and works up to the brain's integration of sensory information

Change Blindness

Definition: Failing to notice changes in the environment

Difference Threshold

Definition: The minimum difference between two stimuli required for detection 50 percent of the time. We experience the difference threshold as a just noticeable difference. (Also called just noticeable difference or JND.)

Inattentional Blindness

Definition: Failing to see visible objects when our attention is directed elsewhere

Perception

Definition: The process of organizing and interpreting sensory information, enabling us to recognize meaningful objects and events.

Priming

Definition: The activation, often unconsciously, of certain associations, thus predisposing one's perception, memory, or response.

Psychophysics

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

Selective Attention

Definition: The focusing of conscious awareness on a particular stimulus

Sensation

Definition: The process by which our sensory receptors and nervous system receive and represent stimulus energies from our environment.

Sensory Adaptation

Definition: Diminished sensitivity as a consequence of constant stimulation

Signal Detection Theory

Definition: 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

Definition: Below one's absolute threshold for conscious awareness

Top-Down Processing

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

Transduction

Definition: 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.

Weber's Law

Definition: The principle that, to be perceived as different, two stimuli must differ by a constant minimum percentage

Extrasensory Perception

Definition: The controversial claim that perception can occur apart from sensory input; includes telepathy, clairvoyance, and precognition

Parapsychology

Definition: The study of paranormal phenomena, including ESP and psychokinesis

Perceptual Set

Definition: A mental predisposition to perceive one thing and not another

Accomodation

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

Lens

Definition: The transparent structure behind the pupil that changes shape to help focus images on the retina.

Cones

Definition: Retinal receptor cells that are concentrated near the center of the retina and that function in daylight or in well-lit conditions. The cones detect fine detail and give rise to color sensations.

Opponent-Process Theory

Definition: 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

Fovea

Definition: The central focal point in the retina, around which the eye's cones cluster.

Optic Nerve

Definition: The nerve that carries neural impulses from the eye to the brain

Intensity

Definition: The amount of energy in a light or sound wave, which we perceive as brightness or loudness, as determined by the wave's amplitude.

Parallel Processing

Definition: The processing of many aspects of a problem simultaneously; the brain's natural mode of information processing for many functions, including vision. Contrasts with the step-by-step (serial) processing of most computers and of conscious problem solving.

Blind Spot

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

Feature Detectors

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

Hue

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

Iris

Definition: A ring of muscle tissue that forms the colored portion of the eye around the pupil and controls the size of the pupil opening.

Pupil

Definition: The adjustable opening in the center of the eye through which light enters.

Retina

Definition: 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.

Rods

Definition: Retinal receptors that detect black, white, and gray; necessary for peripheral and twilight vision, when cones don't respond.

Wavelength

Definition: The distance between a point on one wave and the identical point on the next wave.

Young-Helmholtz Trichromatic Theory

Definition: The theory that the retina contains three different color receptors—one most sensitive to red, one to green, one to blue—which combined can produce the perception of any color.

Binocular Cues

Definition: Depth cues, such as retinal disparity, that depend on the use of two eyes

Monocular Cues

Definition: Depth cues, such as interposition and linear perspective, available to either eye alone

Depth Perception

Definition: The ability to see objects in three dimensions although the images that strike the retina are two-dimensional; allows us to judge distance

Figure-Ground

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

Gestalt

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

Grouping

Definition: the perceptual tendency to organize stimuli into coherent groups

Color Constancy

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

Perceptual Adaptation

Definition: In vision, the ability to adjust to an artificially displaced or even inverted visual field

Perceptual Constancy

Definition: Perceiving objects as unchanging (having consistent lightness, color, shape, and size) even as illumination and retinal images change

Phi Phenomenon

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

Retinal Disparity

Definition: a binocular cue for perceiving depth; by comparing images from the two eyeballs, the brain computes distance - the greater the disparity (difference) between the two images, the close the object

Visual Cliff

Definition: A laboratory device for testing depth perception in infants and young animals

Audition

Definition: The sense or act of hearing

Frequency

Definition: How many wave peaks pass a certain point per given time

Cochlear Implant

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

Conduction Hearing Loss

Definition: Hearing loss caused by damage to the mechanical system that conducts sound waves to the cochlea

Cochlea

Definition: A coiled, bony, fluid-filled tube in the inner ear through which sound waves trigger nerve impulses

Frequency Theory

Definition: 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

Inner Ear

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

Middle Ear

Definition: 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

Pitch

Definition: A tone's experienced highness or lowness; depends on frequency.

Place Theory

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

Sensorineural Hearing Loss

Definition: Hearing loss caused by damage to the cochlea's receptor cells or to the auditory nerves; also called nerve deafness

Embodied Cognition

Definition: In psychological science, the influence of bodily sensations, gestures, and other states on cognitive preferences and judgments

Gate-Control Theory

Definition: 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.

Kinesthesia

Definition: The system for sensing the position and movement of individual body parts

Sensory Interaction

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

Vestibular Sense

Definition: The sense of body movement and position, including the sense of balance