| Term | Definition |
|---|
| Sensation | Process in which the sense organs' receptor cells are stimulated and relay initial information to higher brain centers for further processing. |
| Perception | Process by which an organism selects and interprets sensory input so that it acquires meaning. |
| Psychophysics | Subfield of psychology that focuses on the relationship between physical stimuli and people's conscious experiences of them. |
| Absolute threshold | The statistically determined minimum level of stimulation necessary to excite a perceptual system. |
| Subliminal perception | Perception below the threshold of awareness. |
| Signal Detection Theory | Theory that holds that an observer's perception depends not only on the intensity of a stimulus but also on the observer's motivation, the criteria he or she sets for determining that a signal is present, and on the background noise. |
| Electromagnetic Radiation | The entire spectrum of waves initiated by the movement of charged particles. |
| Light | The small portion of the electromagnetic spectrum that is visible to the human eye. |
| Myopic | Able to see clearly things that are close but having trouble seeing objects at a distance; nearsighted. |
| Hyperopic | Able to see objects at a distance clearly but having trouble seeing things up close; farsighted |
| Photoreceptors | The light-sensitive cells in the retina- the rods and cones. |
| Transduction | Process by which a perceptual system analyzes stimuli and converts them into electrical impulses; also known as coding. |
| Visual cortex | The most important area of the brain's occipital lobe, which receives and further processes information from the lateral geniculate nucleus; also known as the striate cortex. |
| Dark adaptation | The increase in sensitivity to light that occurs when the illumination level changes from high to low, causing chemicals in the rods and cones to regenerate and return to their inactive state. |
| Optic chiasm | Point at which half of the optic nerve fibers from each eye cross over and connect to the other side of the brain. |
| Receptive fields | Areas of the retina that, when stimulated, produce a change in the firing of cells in the visual system. |
| Saccades | Rapid voluntary movements of the eyes. |
| Hue | The psychological property of light referred to as color, determined by the wavelengths of reflected light. |
| Brightness | The lightness or darkness of reflected light, determined in large part by the light's intensity. |
| Saturation | The depth and richness of a hue determined by determined by the homogeneity of the wavelengths contained in the reflected light; also known as purity. |
| Trichromatic theory | Visual theory, stated by Young and Helmholtz that all colors can be made by mixing the three basic colors: red, green, and blue; a.k.a the Young-Helmholtz theory. |
| Color Blindness | The inability to perceive different hues. |
| Opponent-process theory | Visual theory, proposed by Herring, that color is coded by stimulation of three types of paired receptors; each pair of receptors is assumed to operate in an antagonist way so that stimulation by a given wavelength produces excitation (increased firing) in one receptor of the pair and also inhibits the other receptor. |
| Trichromats | People who can perceive all three primary colors and thus can distinguish any hue. |
| Monochromats | People who cannot perceive any color, usually because their retinas lack cones. |
| Dichromats | People who can distinguish only two of the three basic colors. |
| Size constancy | Ability of the visual perceptual system to recognize that an object remains constant in size regardless of its distance from the observer or the size of its image on the retina. |
| difference threshold | minimum difference between any two stimuli that person can detect 50% of the time |
| just noticeable difference (JND) | experience of the difference threshold |
| cornea | transparent covering of the eye |
| iris | colored part of the eye that regulates size of pupil |
| pupil | small opeing in iris that is smaller in bright light and larger in darkness |
| lens | structure behind pupil that changes shape to focus light rays onto the retina |
| retina | light-sensitive surface on back of eye containing rods and cones |
| fovea | small area of retina where image is focused |
| photoreceptors | light sensitive cells (rods and cones) that convert light to electrochemical impulses |
| rods | photoreceptors that detect black, white, and gray, and movement; used for vision in dim light |
| cones | photoreceptors that detect color and fine detail in bright-light conditions; not present in peripheral vision |
| optic nerve | carries impulses from the eye to the brain |
| visual acuity | sharpness of vision |
| blind spot | area on retina with no receptor cells (where optic nerve leaves the eye) |
| parallel processing | simultaneously analyzing different elements of sensory information, such as color, brightness, shape, etc. |
| sensory adaptation | temporary decrease in sensitivity to a stimulus that occurs when stimulation is unchanging |
| frequency | number of wavelengths that pass a point in a given amount of time; determines hue of light and the pitch of a sound |
| audition | the sense of hearing |
| pitch | the highness or lowness of a sound |
| timbre | the quality of a sound determined by the purity of a waveform |
| sound localization | the process by which the location of sound is determined |
| cochlea | snail-shaped fluid-filled tube in the inner ear involved in transduction |
| gate control theory | pain is only experienced in the pain messages can pass through a gate in the spinal cord on their route to the brain |
| kinesthesis | body sense that provides information about the position and movement of individual parts of the body |
| vestibular sense | body sense of equilibrium and balance |
| gustation | sense of taste |
| olfaction | sense of smell |
| selective attention | focused awareness of only a limited amount of all you are capable of experiencing |
| bottom-up processing | information processing that begins at the sensory receptors and works up to perception |
| top-down processing | information processing guided by pre-existing knowledge or expectations to construct perceptions |
| monocular cues | depth cues that are based on one eye |
| binocular cues | depth cues that are based on two eyes |
| ESP | the controversial claim that sensation can occur apart from sensory input |
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