Sensation and Perception

• sensation- stimulation of sensory receptors and the transmission of sensory information to the central nervous system.
• sensory receptors- located in sensory organs such as the eyes and ears, the skin, and elsewhere in the body.
• perception- sensations are organized into an inner representation of the world.
• absolute threshold- minimal amount of energy that can produce a sensation.
• pitch- highness or lowness, determined by the frequency of the sound waves.
• subliminal stimulation- sensory stimulation below a person's absolute threshold for conscious perception.
• difference threshold- minimal difference in intensity required between two sources of energy so that they will be perceived as being different.
• weber's constant- fraction of the intensity by which a source of physical energy must be increased or decreased so that a difference in intensity will be perceived.
• just noticeable difference- minimal amount by which a source of energy must be increased or decreased so that a difference in intensity will be perceived.
• signal-detection theory- perception of sensory stimuli involves the interaction of physical, biological, and psychological factors.
• feature detectors- neurons in the sensory cortex that fire in response to specific features of sensory information.
• sensory adaptation- organisms become more sensitive to stimuli that are low in magnitude and less sensitive to stimuli that are constant or ongoing in magnitude.
• sensitization- positive adaptation, more sensitive to stimuli that are low in magnitude.
• desensitization- negative adaptation, less sensitive to constant stimuli.
• selective attention theory- which information will be granted access to process and which will be ignored.
• automaticity theory- the brain prefers to read the words over the colors because reading is an automatic process.
• speed of processing theory- process written words faster than we can process colors.
• parallel distributed theory- the brain creates different pathways for different tasks.
• vision- "windows on the world" because it is our dominant sense.
• visible light- part of electromagnetic spectrum that stimulate the eye and produces visual sensations.
• hue- the color of light, as determined by its wavelength.
• cornea- transparent tissue forming the outer surface of the eyeball.
• iris- a muscular membrane whose dilation regulates the amount of light that enters the eye.
• pupil- black-looking opening in the center of the iris, through which light enters the eye.
• lens- transparent body behind the iris that focuses an image on the retina.
• retina- area of the inner surface of the eye that contains rods and cones.
• photoreceptors- cells that respond to light.
• bipolar cells- conduct neural impulses from rods and cones to ganglion cells.
• ganglion cells- neurons whose axons form the optic nerve.
• optic nerve- transmit sensory information from the eye to the brain.
• rods- rod-shaped photoreceptors that are sensitive only to the intensity of light.
• cones- cone-shaped photoreceptors that transmit sensations of color.
• fovea- near the center of the retina that is dense with cones and where vision is consequently most acute.
• blind spot- axons from ganglion cells meet to form the optic nerve.
• visual acuity- sharpness of vision.
• presbyopia- a condition characterized by brittleness of the lens.
• dark adaptation- adjusting to conditions of lower lighting by increasing the sensitivity of rods and cones.
• saturation- refers to how intense a color appears to us.
• complementary- descriptive of colors of the spectrum that when combined produce white or nearly white light.
• afterimage- the lingering visual impression made by a stimulus that has been removed.