unit 3

• Sensation


  the process by which our sensory receptors and nervous system receive and represent stimulus energies from our environment.
• Perception


  the process of organizing and interpreting sensory information; enabling us to recognize meaningful objects and events.
• Bottom-up processing


  analysis that begins with the sense receptors and works up to the brain's integration of sensory information.
• Top-down processing


  information processing guided by higher-level mental process, as when we construct perceptions drawing out our experience and expectation.
• Absolute threshold


  the minimum stimulation needed to detect a particular stimulus 50 percent of the time.
• Signal detection theory


  a theory predicting how and when we detect the presence of a faint stimuli ("signal") amid background stimulation ("noise"). Assume that there is no single absolute threshold and that focuses more on the processing of briefly stored information. (e.g. what determines a "hit", "miss," "false alarm" or "correct rejection")
• Difference threshold


  the minimum difference between two stimuli required for detection 50 percent of the time. We experience the difference threshold as a just noticeable difference (also called just noticeable difference or JND.)
• Subliminal Sensation


  detection of stimuli below absolute threshold
• Weber's law

  the principle that, to be perceived as different, two stimuli must differ by a constant minimum percentage (rather than a constant amount).
• Sensory Adaptation

  diminished sensitivity as a consequence of constant stimulation.
• Transduction

  conversion of one form of energy into another. In sensation, the transforming of stimulus energies into neural impulses.
• Wavelength

  the distance from the peak of one light or sound wave to the peak of the next. Electromagnetic wavelengths vary from the short blips of cosmic rays to the long pulses of radio transmission.
• Hue

  the dimension of color that is determine by the wavelength of light; what we know as the color names blue, green, and so forth.
• Pupil


  the adjustable opening in the center of the eye through which light enters.
• Iris


  a ring of muscle tissue that forms the color portions of the eye around the pupil and controls the size of the pupil opening.
• Lens


  the transparent structure behind the pupil that changes shape to help focus images on the retina.
• Accommodation


  the process by which the eye's lens changes shape to focus near or far objects on the retina.
• Retina


  the light-sensitive inner surface of the eye, containing the receptor rods and cones plus layers of neurons that begin the processing of visual information.
• Acuity


  the sharpness of vision.
• Nearsightedness


  a condition in which nearby objects are seen more clearly than distant objects because distant objects focus right in front of the retina.
• Farsightedness


  the condition in which faraway objects are seen more clearly that near objects because the image of near objects is focused behind the retina.
• Rods


  retinal receptors that detect black, white, and gray; necessary for peripheral and twilight vision, when cones don't respond.
• Cones


  receptors cells that are concentrated near the center of the retina and that function in daylight or in well-lit conditions. The cones detect fine details and give rise to color sensation.
• Optic nerve


  the nerve that carries neural impulses from the eye to the brain.
• Blind spot


  the point at which the optic nerve leaves the eye; no receptors cells are located there. Creates a gap in our vision that is "filled" by the brain.
• Fovea


  the central focal point in the retina, around which the eye's cones cluster.
• Feature detectors


  nerve cells in the brain that respond to specific features of the stimuli, such as shape, angle, or movement.
• Parallel processing


  the processing of several aspects of a problem simultaneously; the brain's natural mode of information processing for many functions, including vision. Contrast with the step-by-step (serial) processing of most computers and of conscious problem solving.
• Young-Helmholtz Trichromatic theory


  the theory that the retina contains three different colors receptors-one most sensitive to red, one to green, one to blue-which when stimulated in combination can produce the perception of any color.
• Opponent-Process theory


  the theory that opposing retinal processes (red-green, yellow-blue, white-black) enable color vision; useful for explaining the phenomenon of "after-images"
• Color constancy


  perceiving familiar objects as having consistent color, even if changing illumination alters the wavelengths reflected by the objects.
• Audition


  the sense of hearing
• Frequency


  the number of complete wavelengths that pass a point in a given time.
• Middle ear


  the chamber between the eardrum and cochlea containing three tiny bones (hammer, anvil, and stirrup) that concentrate the vibrations of the eardrum on the cochlea's oval window.
• Inner ear


  the innermost part of the ear, containing the cochlea, semicircular canals, and vestibular sacs.
• Cochlea


  a coiled bony, fluid-filled tube in the inner ear through which sound waves trigger nerve impulses.
• Place Theory


  in hearing, the theory that links the pitch we hear with the place where the cochlea's membrane is stimulated.
• Frequency theory


  in hearing, the theory that the rate of nerve impulses traveling up the auditory nerve matches the frequency of a tone, thus enabling us to sense its pitch.
• Gate-Control theory


  the theory that the spinal cord contains neurological "gate" that blocks pain signals or allows them to pass on to the brain. The "gate" is open by the activity of pain signals traveling up small nerve fibers and is closed by activity in larger fibers or by information coming form the brain.
• Kinesthesis


  the system for sensing the position and movement of individual body parts; enabled by feedback from proprioceptors (which provide info about the movement of muscles, tendons, joints)