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absolute threshold
The minimum amount of physical energy required to produce a sensation.
aerial perspective
Monocular depth cue in which we use brightness, color, and detail to determine distance; closer objects tend to look brighter.
amacrine cells
With the horizontal cells, they interconnect the neurons in the retina.
ambiguous figure
Perceptual ambiguity in which the figure and ground seem to reverse themselves.
amplitude
Intensity of sound waves; amplitude determines loudness of sound.
Anosmia
loss of ability to smell.
aphasia
Disorder in which a person loses the ability to understand speech.
apparent motion
Perceived movement of an object when in fact there is none; a visual illusion.
auditory canal
Canal leading from the outer ear into the middle ear.
auditory nerve
Nerve that carries auditory information from the ear to the brain.
autokinetic effect
Perception of movement of a stationary spot of light in a darkened room.
basilar membrane
Partition in the cochlea of the ear; involved in sound sensation.
binaural
Condition in which sound is delivered to both ears simultaneously.
binocular depth cues
Visual cues that depend on both eyes; used to detect distance.
bipolar cells
Cells in the retina of the eye; light causes the rods and cones to send electrical energy to the bipolar cells, then pass on neural impulses to ganglion cells.
blind spot
Place in the retina where the optic nerve begins; a person cannot see at this location.
brightness constancy
Tendency to see objects as continuing to have the same brightness even though light or shadow may change their immediate sensory properties.
chemical senses
The sense of smell and taste; sensory stimulation of the chemical sense receptors involves contact with chemical substances.
closure
Perceptual principle of organization of filling in the gaps in a figure to perceive a complete form.
cochlea
A spiraled organ in the inner ear that is involved in sound sensation.
color constancy
Tendency to see familiar objects as the same color regardless of the illumination.
common fate
Gestalt perceptual principle in which groups of stimuli, or objects moving together, are seen as a unit.
cones
One type of vision receptor; cones respond to color variations in bright light.
continuity
The Gestalt rule of perceiving a straight line as continuing to be straight.
convergence
Binocular depth cue in which we detect distance by interpreting the kinesthetic sensations produced by the muscles of the eyeballs.
cornea
Outer membrane that covers the eyeball.
dark adaptation
Process in which the retina's rods and cones adjust to changes in dim light.
decibel
Unit for measuring loudness.
depth perception
Ability to judge distance to object.
difference threshold
The minimum amount of energy change required to produce a difference in sensation.
eardrum
Thin membrane stretched across the inner end of the auditory canal.
figure-ground relationship
Perceptual organization rule that explains our tendency to separate a scene into a main figure and a background.
flavor
Property of food that is due to smell, appearance, texture, and temperature.
fovea
The middle area of the retina in which the cones are clustered.
frequency theory of hearing
Theory of hearing that states that the frequency of vibrations at the basilar membrane determines the frequency of firing of neurons carrying impulses to the brain.
ganglion cells
Cells in the retina of the eye; the ganglion cells receive messages from the bipolar cells. Axons of the ganglions form the optic nerve.
gate-control theory of pain
Theory of pain that proposes that there is a gate that allows pain impulses to travel from the spinal cord to the brain.
haptic sense
Sense of touch.
horizontal cells
The cells that interconnect the neurons in the retina.
hue
The color we perceive; hue is determined by the wavelength of light.
illusion
An incorrect perception that occurs when sensation is distorted.
impossible figure
A figure that logically cannot exist; a visual illusion.
induced movement
Situation in which we attribute motion to an object that is not really moving; when we incorrectly attribute motion to figure rather than background.
interposition
Monocular depth cue in which one object partially blocks another; we assume the overlap is due to the first one being closer.
just noticeable difference (JND)
Difference threshold: minimum amount of energy required to produce a difference in sensation.
kinesthesis
The sense of bodily movement.
lens
Part of the eye that focuses on stimuli.
light waves
A type of electromagnetic energy; light waves stimulate the eyes to produce vision.
linear perspective
Monocular depth cue in which lines converging depict distance; example is railroad tracks receding in the distance.
monaural
Condition in which sound is delivered only to one ear.
monocular depth cues
Visual cues that depend on only one eye; used to detect distance.
motion parallax
Monocular depth cue where objects close by seem to move faster than objects farther away.
Muller-Lyer illusion
A well-known illusion, in which two horizontal lines have end lines either going in or out; the line with the end lines going in appears longer.
nanometer (nm)
One billionth of a meter.
Necker cube
A visual illusion. The Necker cube is a drawing of a cube designed so that it is difficult to determine which side is toward you.
occipital lobe
Part of the cerebral cortex of the brain that is involved in interpreting visual sensations.
olfaction
The smell sense.
olfactory epithelium
Sense receptor for smell that reacts chemically with odors to produce neural impulses.
opponent-process theory of color vision
Theory of color vision that postulated the existence of receptors sensitive to opposing pairs of colors.
optic chiasma
Junction in the optic nerve that connects the nerve tracts from each eye carrying information from the same side of the visual field.
optic nerve
Nerve that travels from the retina of the eye to the brain.
organ of Corti
Sensory receptor for sound.
papillae
Small bumps on the surface of the tongue that contain the taste buds.
paradoxical cold
A phenomenon in which a person sometimes senses warm stimuli of 45 C 112 F as cold.
perception
The active process in which the sensory information that is carried through the nervous system to the brain is organized and interpreted; the interpretation of sensation.
perceptual constancy
The tendency to perceive objects in a consistent manner despite the changing sensations received by sense organs; constancy plays an important role in helping us to adapt to the environment successfully.
periaqueductal gray (PAG)
In a theory of pain, the area of the brainstem that produces endorphins that then inhibit the neurons in the spinal cord from transmitting pain.
perspective
Changes in the appearance of objects or surfaces as the distance from the perceiving increases; monocular depth cues help us perceive distance correctly.
phi phenomenon
Perception of movement between two lights that are alternately going on and off; @i{see} stroboscopic motion.
pinna
Large flap of outer ear.
place theory
Emphasizes the place on the basilar membrane that produces pitch differences.
Poggendorff illusion
Illusion in which a straight line looks distorted.
Ponzo illusion
An illusion in linear perspective where a line that looks larger is actually closer.
Pragnanz (law of)
Gestalt psychologist law that states that people have a tendency to group stimuli according to rules, and that people do this whenever possible.
pressure
In sensation, the skin sense that detects contact on the skin. In psychology, what we experience when we strive to meet the social and psychological demands placed upon us; internal pressure results from self-demands, while external pressure results from demands from others.
projective personality test
A personality test that presents ambiguous stimuli to which subjects are expected to respond with projections of their own personality.
proximity
Closeness in time and space. In perception, it is the Gestalt perceptual principle in which stimuli next to one another are included together.
psychophysics
An area of psychology in which researchers compare the physical energy of a stimulus with the sensation reported.
pupil
Part of the eye that adjusts to light intensities; when the pupil constricts, less light is permitted into the eye.
real motion
In perception, a situation in which we correctly perceive an object as moving.
retina
A patch of tissue in which lie the rods and cones of the eye; the "film" of the eye.
retinal disparity
Binocular cue in which each eye receives slightly different sensory information that must be combined for normal vision.
rhodopsin
Photosensitive pigment that breaks down into chemicals that stimulate neurons sending visual messages to the brain.
rods
One type of vision receptor; rods respond to differences in brightness but not to color variations.
selective attention
The perception process of screening out irrelevant information while focusing on significant stimuli in the environment.
semicircular canals
Canals in the inner ear that are receptors for the vestibular sense.
sensation
The passive process in which stimuli are received by sense receptors and transformed into neural impulses that can be carried through the nervous system; first stage in becoming aware of environment.
sense receptors
Structures at the end of neurons directly affected by environmental stimuli.
sensory adaptation
Tendency of the sense organs to adjust to continuous stimulation by reducing their functioning; a stimulus that once caused sensation and no longer does.
shape constancy
The tendency to perceive familiar objects as having a permanent shape, even if we look at the objects from different angles.
similarity
Gestalt principle in which similar stimuli are perceived as a unit.
size constancy
Tendency to perceive objects as the same size even though the retinal size changes.
size perspective
Monocular depth cue in which we normally interpret distance by the relative size of an object; the smaller an object, the farther away it seems.
sound waves
Rapid changes in air pressure caused by vibrating object in contact with the air.
stroboscopic movement
Perception of movement when a series of still pictures are seen rapidly; each successive one is slightly different from the earlier one; the basis of movies.
taste buds
Receptors for sense of taste; taste buds are located on top and sides of the tongue.
texture gradient
Monocular depth cue in which small objects close to us show more detail than objects farther away.
timbre
Complexity of the mixture of sound waves.
trichromatic theory
Young-Helmholtz idea of color vision.
vestibular sense
Sense that helps keep our balance.
visual capture
The tendency for vision to dominate the other senses.
wave amplitude
The height of a light wave (amplitude) determines the experience of brightness.
wavelength
The wavelength of light waves is the distance between any point on a wave and the corresponding point of the wave in the next cycle; wavelength determines experience of hue.
Weber's Law
Law that states that the difference threshold depends on the ratio of the intensity of one stimulus to another rather than on an absolute difference.
Wernicke's area
Area of the brain important in speech perception.