Sensation and Perception Definitions

Chapter 3

SENSATION: The experience of sensory stimulation
RECEPTOR CELL: a specialized cell that responds to a particular type of energy
PERCEPTION: the process of creating meaningful patterns from raw sensory information
ABSOLUTE THRESHOLD the least amount of energy that can be detected as a stimulation 50% of the time
ADAPTATION: adjustment of the senses to the level of stimulation they are receiving
DIFFERENCE THRESHOLD-JUST NOTICEABLE DIFFERENCE (JND) smallest change in stimulation detected 50% of the time
WEBER'S LAW: the JND for any given sense is a constant fraction or proportion of the stimulation being judged
CORNEA: transparent protective coating over front of eye
PUPIL: small opening in iris through which light enters
IRIS: coloured part of eye
LENS: transparent part of eye inside pupil that focuses light onto retina
RETINA: lining of eye containing receptor cells sensitive to light
FOVEA: area of retina that is centre of visual field
RODS: receptor cells in retina responsible for night vision and perception of brightness- best low light
CONES: receptor cells in retina responsible for colour vision (less sensitive to light) best in bright light -concentrated in fovea
BIPOLAR CELLS: neurons that have only one axon and one dendrite; in the eye these neurons connect the receptors on the retina to the ganglion cell
VISUAL ACUITY: ability to distinguish fine details visually
DARK ADAPTATION: increased sensitivity of cones and rods in darkness
LIGHT ADAPTATION: Decreased sensitivity of cones and rods in bright light
AFTERIMAGE: sense experience that occurs after visual stimulus has been removed
GANGLION CELLS: neurons that connect bipolar cells in eyes to the brain
OPTIC NERVE: bundle of axons of ganglion cells that carries neural messages from each eye to brain
BLIND SPOT: place on retina where axons of all ganglion cells leave eye and where there are no receptors
OPTIC CHASM point near base of brain where some fibres in optic nerve from each eye cross to other side of brain
HUE: aspect of colour corresponds to names such as blue, red, green,yellow
SATURATION: vividness or richness of a hue
BRIGHTNESS: nearness of colour to white as opposed to black


process of mixing lights of different wavelengths to create new hue
SUBTRACTIVE COLOUR MIXING: mixing paint pigments, each absorbs some wavelengths of light and reflects others
TRICHROMATIC THEORY: all colour perception derives from three different colour receptors ( usually red,green, blue)
OPPONENT-PROCESS THEORY: three sets of colour receptors (yellow-blue, red-green,black-white) respond to determine the colour experienced
COLOUR BLINDNESS: partial or total inability to perceive hues
FREQUENCY: number of cycles per second in wave; in sound determines pitch - how high or low sound is -measured in HERTZ
HERTZ: cycles per second; unit of measurement for frequency
AMPLITUDE: magnitude of wave; in sound determines loudness -measured in decibels
DECIBEL: unit of measurement for loudness of sounds
OVERTONES: tones that result from sound waves that are multiples of basic tone; primary determinant of timbre
TIMBRE: the quality of texture of sound, caused by overtones
AUDITORY NERVE: bundle of axons that caries signals from each ear to the brain
OVAL WINDOW: membrane across the opening between the middle ear and inner ear that conducts vibrations to the cochlea
COCHLEA: part of inner ear containing fluid that vibrates which in turn causes basilar membrane to vibrate
BASILAR MEMBRANE: vibrating membrane in the cochlea of the inner ear; it contains sense receptors for sound
PLACE THEORY: pitch determined by the location of greatest vibration on the basilar membrane -high frequency cause greatest vibration at stiff base of basilar membrane-low frequency at opposite end
FREQUENCY THEORY: pitch is determined by the frequency with which hair cells in the cochlea fire
VOLLEY PRINCIPLE: refinement of frequency theory-receptors in ear fire in sequence with one group responding, then a second, then a third and so on, so that complete pattern of firing corresponds to the frequency of the sound wave
OLFACTORY BULB: smell centre in brain
PHEROMONES: chemical that communicates information to other organisms through smell-pheromones can have specific and powerful effects on behaviour
TASTE BUDS: structures on tongue that contain the receptor cells for taste
KINESTHETIC SENSES: senses of muscle movement, posture, and strain on the muscles and joints
VESTIBULAR SENSES: the senses of equilibrium and body position in space
GATE CONTROL THEORY: the theory that a neurological gate in the spinal cord controls the transmission of pain messages to the brain-if gate open experience more pain

subject given neutral pill and subject reports feeling better-release endorphins-pain blocking neurotransmitters


PERCEPTION deciphering meaningful patterns in complex sensory information
PERCEPTUAL CONSTANCY tendency to perceive objects as stable, unchanging despite changes in sensory stimulation
SIZE CONSTANCY perception of object as same size regardless of distance from which it is viewed
SHAPE CONSTANCY tendency to see an object as same shape no matter what angle it is viewed from
BRIGHTNESS CONSTANCY perception of brightness as same even though amount of light on retina changes
COLOUR CONSTANCY inclination to perceive familiar objects as retaining their colour despite changes in sensory information
MONOCULAR CUES visual cues requiring one eye: superposition, linear perspective, aerial perspective,elevation, texture gradient, shadowing and motion parallax
SUPERPOSITION monocular distance cue where one object by partly blocking a second object is perceived as being closer
LINEAR PERSPECTIVE monocular cue to distance and depth based on fact that two parallel lines seem to come together in horizon
AERIAL PERSPECTIVE: monocular cue to distance and depth based on fact that more distant objects are likely to appear hazy and blurred
ELEVATION monocular cue to distance and depth based on fact that the higher on horizontal plane as object is, the farther away it appears
TEXTURE GRADIENT monocular cue to distance and depth based on the fact that objects seen at greater distances appear to be smoother and less textured
SHADOWING monocular cue to distance and depth based on fact that shadows often appear on the parts of objects that are more distant
MOTION PARALLAX monocular cue where objects closer than the point of visual focus seem to move in the direction opposite to the viewer's moving head and objects beyond the focus point appear to over in the same direction as the viewerÕs head
BINOCULAR CUES: visual cues requiring both eyes
STEREOSCOPIC VISION combination of two retinal images to give a three dimensional perceptual experience
RETINAL DISPARITY binocular distance cue based on the difference between the images cast on the two retinas when both eyes are focused on the same object
CONVERGENCE a visual depth cue that comes from muscles controlling eye movement as the eyes turn inward to view a nearby stimulus
MONAURAL cue to sound location that requires just one ear
BINAURAL cue to sound location that involves both ears together
AUTOKINETIC ILLUSION the perception that a stationary object is actually moving
STROBOSCOPIC MOTION apparent movement results from flashing a series of still pictures rapidly, as in motion picture
PHI PHENOMENON apparent movement caused by flashing lights in sequence as on theatre marquee/neon light