Chapter 6

sensation

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 info, 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

transduction

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.

Psychophysics

the study of relationships between the 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

singular detection theory

a theory prediciting how and when we detect the presence of a faint stimulus amid background stimulation. Assumes there is no single absolute threshold and that detection depends partly on a person's experiance, expectations, motivation, and alertness

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

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

wavelength

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 cosmic rays to the long pulses of radio transmission

hue

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

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

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

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; necessary for peripheral and twilight vision, when cones don't respond

cones

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.

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

fovea

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

Young-Helmholtz trichromatic theory

the theory that the retina contains three different 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

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

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; 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.

gestalt

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

figure-ground

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

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 and convergence, that depend on the use of two eyes

retinal disparity

a binocular cue for perceiving depth by comparing images from the retinas in the two eyes, the brain computes distance—the greater the disparity (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 (having consistent lightness, color, shape, and size) 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 object

perceptual adaptation

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

audition

the sense or act of hearing

frequency

The number of complete waves that pass a given point in a certain amount of 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

cochela

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

sensorinerual hearing loss

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

conduction hearing loss

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

cochlear implant

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

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

nociceptors

sensory receptors that enable the perception of pain in response to potentially harmful stimuli

gate-control theory

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.

hypnosis

a social interaction in which one person suggests to another that certain perceptions, feelings, thoughts, or behaviors will spontaneously occur

dissociation

a split in consciousness, which allows some thoughts and behaviors to occur simultaneously with others

posthypnotic suggestion

a suggestion, made during a hypnosis session, to be carried out after the subject is no longer hypnotized; used by some clinicians to help control undesired symptoms and behaviors

kinesthesia

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

vestibular sense

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

sensory interaction

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

embodied cognition

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