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Psychology, 5/e

Lester M. Sdorow, Arcadia University
Cheryl A. Rickabaugh, University of Redlands

Sensation and Perception

absolute threshold	The minimum amount of stimulation that an individual can detect through a given sense.



accommodation	The process by which the lens of the eye increases its curvature to focus light from close objects or decreases its curvature to focus light from more distant objects.



acupuncture	A pain-relieving technique that relies on the insertion of fine needles into various sites on the body.



audition	The sense of hearing.



auditory cortex	The area of the temporal lobes that processes sounds.



auditory nerve	The nerve that conducts impulses from the cochlea to the brain.



basilar membrane	A membrane running the length of the cochlea that contains the auditory receptor (hair) cells.



binocular cues	Depth perception cues that require input from the two eyes.



brightness constancy	The perceptual process that makes an object maintain a particular level of brightness despite changes in the amount of light reflected from it.



clairvoyance	The alleged ability to perceive objects or events without any sensory contact with them.



cochlea	The spiral, fluid-filled structure of the inner ear that contains the receptor cells for hearing.



color afterimage	A visual image that persists after the removal of a visual stimulus.



color blindness	The inability to distinguish between certain colors, most often red and green.



conduction deafness	Hearing loss usually caused by blockage of the auditory canal, damage to the eardrum, or deterioration of the ossicles of the middle ear.



cones	Receptor cells of the retina that play an important role in daylight vision and color vision.



cornea	The round, transparent area in the front of the sclera that allows light to enter the eye.



dark adaptation	The process by which the eyes become more sensitive to light when under low illumination.



depth perception	The perception of the relative distance of objects.



difference threshold	The minimum amount of change in stimulation that can be detected.



extrasensory perception (ESP)	The alleged ability to perceive events without the use of sensory receptors.



feature-detector theory	The theory that we construct perceptions of stimuli from activity in neurons of the brain that are sensitive to specific features of those stimuli.



figure-ground perception	The distinguishing of an object (the figure) from its surroundings (the ground).



fovea	A small area at the center of the retina that contains only cones and provides the most acute vision.



frequency theory	The theory of pitch perception that assumes that the basilar membrane vibrates as a whole in direct proportion to the frequency of the sound waves striking the eardrum.



gate-control theory	The theory that pain impulses can be blocked by the closing of a neuronal gate in the spinal cord.



gustation	The sense of taste, which detects molecules of substances dissolved in the saliva.



hyperopia	Visual farsightedness, which is caused by a shortened eyeball.



iris	The donut-shaped band of muscles behind the cornea that gives the eye its color and controls the size of the pupil.



just noticeable difference (jnd)	Weber and Fechner's term for the difference threshold.



kinesthetic sense	The sense that provides information about the position of the joints, the degree of tension in the muscles, and the movement of the arms and legs.



lens	The transparent structure behind the pupil that focuses light onto the retina.



loudness perception	The subjective experience of the intensity of a sound, which corresponds most closely with the amplitude of the sound waves composing it.



mental telepathy	The alleged ability to perceive the thoughts of others without any sensory contact with them.



monocular cues	Depth perception cues that require input from only one eye.



moon illusion	The misperception that the moon is larger when it is at the horizon than when it is overhead.



myopia	Visual nearsightedness, which is caused by an elongated eyeball.



nerve deafness	Hearing loss caused by damage to the hair cells of the basilar membrane, the axons of the auditory nerve, or the neurons of the auditory cortex.



olfaction	The sense of smell, which detects molecules carried in the air.



opponent-process theory	The theory that color vision depends on red-green, blue-yellow, and black-white opponent processes in the brain.



optic chiasm	The point under the frontal lobes at which some axons from each of the optic nerves cross over to the opposite side of the brain.



optic nerve	The nerve, formed from the axons of ganglion cells, that carries visual impulses from the retina to the brain.



otolith organs	The vestibular organs that detect horizontal or vertical linear movement of the head.



parapsychology	The study of extrasensory perception, psychokinesis, and related phenomena.



perception	The process that organizes sensations into meaningful patterns.



pheromone	An odorous chemical secreted by an animal that affects the behavior of other animals.



photopigments	Chemicals, including rhodopsin and iodopsin, that enable the rods and cones to generate neural impulses.



pitch perception	The subjective experience of the highness or lowness of a sound, which corresponds most closely with the frequency of the sound waves that compose it.



placebo	An inactive substance that might induce some of the effects of the drug for which it has been substituted.



place theory	The theory of pitch perception that assumes that hair cells at particular points on the basilar membrane are maximally responsive to sound waves of particular frequencies.



precognition	The alleged ability to perceive events in the future.



prosopagnosia	A form of visual agnosia in which an individual can identify details of faces but cannot recognize faces as wholes.



psychokinesis (PK)	The alleged ability to control objects with the mind alone.



psychophysics	The study of the relationship between the physical characteristics of stimuli and the conscious psychological experiences that are associated with them.



pupil	The opening at the center of the iris that controls how much light enters the eye.



retina	The light-sensitive inner membrane of the eye that contains the receptor cells for vision.



rods	Receptor cells of the retina that play an important role in night vision and peripheral vision.



sclera	The tough, white outer membrane of the eye.



semicircular canals	The curved vestibular organs of the inner ear that detect rotary movements of the head in any direction.



sensation	The process that detects stimuli from the body or surroundings.



sensory adaptation	The tendency of the sensory receptors to respond less and less to a constant stimulus.



sensory receptors	Specialized cells that detect stimuli and convert their energy into neural impulses.



sensory transduction	The process by which sensory receptors convert stimuli into neural impulses.



sex-linked traits	Traits controlled by genes located on the sex chromosomes.



shape constancy	The perceptual process that makes an object appear to maintain its normal shape regardless of the angle from which it is viewed.



signal-detection theory	The theory holding that the detection of a stimulus depends on both the intensity of the stimulus and the physical and psychological state of the individual.



size constancy	The perceptual process that makes an object appear to remain the same size despite changes in the size of the image it casts on the retina.



skin senses	The senses of touch, temperature, and pain.



smooth pursuit movements	Eye movements that track objects.



somatosensory cortex	The area of the parietal lobes that processes information from sensory receptors in the skin.



sound localization	The process by which the individual determines the location of a sound.



subliminal perception	The unconscious perception of stimuli that are too weak to exceed the absolute threshold for detection.



taste buds	Structures lining the grooves of the tongue that contain the taste receptor cells.



timbre	The subjective experience that identifies a particular sound and corresponds most closely to the mixture of sound waves composing it.



transcutaneous electrical nerve stimulation (TENS)	The use of electrical stimulation of sites on the body to provide pain relief, apparently by stimulating the release of endorphins.



trichromatic theory	The theory that color vision depends on the relative degree of stimulation of red, green, and blue receptors.



tympanic membrane	The eardrum; a membrane separating the outer from the middle ear that vibrates in response to sound waves that strike it.



vestibular sense	The sense that provides information about the head's position in space and helps in the maintenance of balance.



visible spectrum	The portion of the electromagnetic spectrum that we commonly call light.



vision	The sense that detects objects by the light reflected from them into the eyes.



visual agnosia	A condition in which an individual can see objects and identify their features but cannot recognize the objects.



visual cortex	The area of the occipital lobes that processes visual input.



visual illusion	A misperception of physical reality usually caused by the misapplication of visual cues.



volley theory	The theory of pitch perception that assumes that sound waves of particular frequencies induce auditory neurons to fire in volleys, with one volley following another.



Weber's law	The principle that the amount of change in stimulation needed to produce a just noticeable difference is a constant proportion of the original stimulus.

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