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sensation The process by which stimulation of a sensory receptor produces neural impulses that the brain interprets. perception the process of organizing and interpreting sensory information, enabling us to recognize meaningful objects and events. 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. sensory adaptation reduced responsiveness caused by prolonged stimulation absolute threshold minimum stimulation needed to detect a particular stimulus 50% of the time difference threshold the smallest change in stimulation that a person can detect 50% of the time Weber's Law the principle which states that the difference threshold is proportional to the intensity of the stimulus signal detection theory 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 detection depends partly on a person's experience, expectations, motivation, and level of fatigue. retina the light-sensitive membrane covering the back wall of the eyeball photoreceptors The light-sensitive cells in the retina- the rods and cones. 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. They detect fine detail and give rise to color sensations. fovea the central focal point in the retina, around which the eye's cones cluster optic nerve the cranial nerve that serves the retina blind spot the point where the optic nerve enters the retina (contains no rods or cones) brightness A psychological sensation caused by the intensity of light waves. color Also called hue, it is not a property of things in the external world. It is a psychological sensation created by the brain from information obtained by the eyes from light waves of visible light. visible spectrum The tiny range of the electromagnetic spectrum that people can see. trichromatic theory idea that color vision is based on our sensitivity to three different colors: blue, green, and red 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 afterimages sensations that linger after the stimulus is removed. Most visual afterimages are negative afterimages, which appear in reversed colors. color blindness a variety of (usually genetic) disorders marked by inability to distinguish some or all colors electromagnetic spectrum arrangement of electromagnetic radiation--including radio waves, visible light from the Sun, gamma rays, X rays, ultraviolet waves, infrared waves, and microwaves--according to their wavelengths frequency the number of complete wavelengths that pass a point in a given time (usually one second) amplitude the height of a wave's crest (usually measured from crest to trough - top to bottom) Tympanic Membrane the eardrum - a tightly stretched sheet of tissue that transfers vibrations to the bones of the inner ear. cochlea a coiled, snail shaped, bony, fluid-filled tube in the inner ear through which sound waves trigger nerve impulses basilar membrane A structure that runs the length of the cochlea in the inner ear and holds the auditory receptors, called hair cells. pitch the property of sound that varies with variation in the frequency of vibration (how high or low the sound is) loudness perception of sound intensity produced by amplitude of the wave timbre The quality of a sound, as distinguished from intensity and pitch. It comes from the sound waves complexity. conduction deafness hearing loss due to problems with the bones of the middle ear nerve deafness hearing loss due to failure of the auditory nerve vestibular sense the sense of body movement and position, including the sense of balance. It is closely associated with the inner ear. kinesthetic sense the sense of body position and movement of body parts relative to each other olfaction the sense of smell pheremones Chemical signals released by organisms to communicate with other members of their species. ________ are often used by animals as sexual attractants. gustation The sense of taste. skin senses sensory senses for processing touch, warmth, cold, texture, and pain Gate control theory theory that spinal cord contains neurological gate that blocks pains signals or allows them to pass. placebo effect a change in a participant's illness or behavior that results from a belief that the treatment will have an effect, rather than the actual treatment percept The meaningful product of perception - often an image that has been associated with concepts, memories of events, emotions, and motives. feature detectors nerve cells in the brain that respond to specific features of the stimulus, such as shape, angle, or movement binding problem question of how the visual, auditory, and other areas of the brain influence one another to produce a combined perception of a single object 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 perceptual constancy perceiving objects as unchanging (having consistent lightness, color, shape, and size) even as illumination and retinal images change illusion a false perception ambiguous figures images that are capable of more than one interpretation. gestalt psychology a psychological approach that emphasizes that we often perceive the whole rather than the sum of the parts. Believed that much of perception is caused by innate characteristics of the brain. figure the part of a pattern that commands attention ground the part of a pattern that does not command attention - A.K.A. the background closure a Gestalt principle of organization holding that there is an innate tendency to perceive incomplete objects as complete and to close or fill gaps and to perceive asymmetric stimuli as symmetric laws of perceptual grouping The Gestalt principles of similarity, proximity, continuity, and common fate. These "laws" suggest how our brains prefer to group stimulus elements together to form a percept law of similarity a Getalt principle of organization holding that (other things being equal) parts of a stimulus field that are similar to each other tend to be perceived as belonging together as a unit law of proximity a Gestalt principle of organization holding that (other things being equal) objects or events that are near to one another (in space or time) are perceived as belonging together as a unit law of continuity The Gestalt principle that we prefer perceptions of connected and continuous figures to disconnected and disjointed ones. law of common fate the Gestalt principle that we tend to group similar objects together that share a common motion or destination law of Pragnanz the Gestalt principle that the simplest organization requiring the least cognitive effort will emerge as the figure binocular cues depth cues, such as retinal disparity and convergence, that depend on the use of two eyes monocular cues depth cues, such as interposition and linear perspective, available to either eye alone learning based inference The view that perception is primarily shaped by learning (or experience), rather than by innate factors. perceptual set A mental readiness to perceive a stimulus in a particular way in a given context