11Vision Structures of the Human Eye CorneaClear outer membrane that bends light to focus it in the eye.PupilThe hole in the iris through which light passes.LensThe structure that focuses light on the retina.
20Vision Opponent-Process Theory Color vision is derived from three pairs of opposing receptors. The opponent colors are blue and yellow, red and green, and black and white.Theory explains afterimages and color deficiency.
30Other Senses Coordination Kinesthetic System Vestibular System Structures distributed throughout body that sense position and movement of body parts.Vestibular SystemThe inner ear and brain structures that afford a sense of equilibrium.
31Keeping the Signals Straight SynesthesiaRare condition in which stimulation in one sensory modality triggers sensations in another sensory modality.Each sensory system designed to operate separately from the others.Selective AdaptationA decline in sensitivity to a stimulus as a result of constant exposure.
36Perceptual Constancies Size ConstancyThe tendency to view an object as constant in size despite changes in the size of the retinal image.Shape ConstancyThe tendency to see an object as keeping its form despite changes in orientation.
39Depth and Dimension Depth Perception Convergence Binocular Disparity The use of visual cues to estimate depth and distance.ConvergenceA binocular cue involving the turning inward of the eyes as an object gets closer.Binocular DisparityA binocular cue whereby the closer an object is, the more different the image is in each retina.
40Depth and Dimension Monocular Depth Cues Distance cues that enable the perception of depth with one eye.Relative Image SizeTexture GradientLinear PerspectiveInterpositionAtmospheric PerspectiveRelative ElevationFamiliarity
49The Continuing Controversy The ganzfield procedureResearchers disagree about the reliability of studies done to replicate the ganzfield test.Visit for information about the James Randi Educational Foundation’s million-dollar paranormal challenge.