the process by which our sensory receptors and nervous system receive and represent stimulus energies from our environment
the process of organizing and interpreting sensory information, enabling us to recognize meaningful objects and events
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 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.
below one's absolute threshold for conscious awareness
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 ind.)
the principle that, to be perceived as different, two stimuli must differ by a constant minimum percentage (rather than a constant amount)
diminished sensitivity as a consequence of constant stimulation
conversion of one form of energy into another. In sensation, the transforming of stimulus energies into neural impulses
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.
the dimension of color that is determined by the wavelength of light; what we know as the color names blue, green, and so forth
the amount of energy in a light or sound wave, which we perceive as brightness or loudness, as determined by the wave's amplitude
the adjustable opening in the center of the eye through which light enters
a ring of muscle tissue that forms the colored portion of the eye around the pupil and controls the size of the pupil opening
the process by which the eye's lens changes shape to focus near or far objects on the retina
the sharpness of vision
a condition in which nearby objects are seen more clearly than distant objects because distant objects focus in front of the retina
a condition in which faraway objects are seen more clearly than near objects because the image of near objects is focused behind the retina
retinal receptors that detect black, white, and gray; necessary for peripheral and twilight vision, when cones don't respond
retinal receptor cells that are concentrated near the center of the retina and that function in daylight or in well-lit conditions. The cones detect fine detail and give rise to color sensations.
the nerve that carries neural impulses from the eye to the brain
the central focal point in the retina, around which the eye's cones cluster
young-helmholtz trichromatic (three color) theory
the theory that the retina contains three different color 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. For example, some cells are stimulated by green and inhibited by red; others are stimulated by red and inhibited by green
perceiving familiar objects as having consistent color, even if changing illumination alters the wavelengths reflected by the object
the sense of hearing
conduction hearing loss
sensorineural hearing loss
gate control theory