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Size constancy
Size constancy The fact that the perception of the sizes of objects remains remarkably constant at varying distance despite the fact that the image projected on the retina changes.
RELATED TERMS--------------------------------------
Retina
A membrane lining the inside of the back of the eye that contains light-sensitive nerve cells that convert focused light into nerve impulses, making vision possible.
SIMILAR TERMS--------------------------------------
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Sensory fusion
The combining of drawing together of two images which fall on different points in the two retinas without changing the vergence of the two eyes.
Short-Sightedness
See Myopia.
Short-term visual store
Visual memory not affected by masking, not in anatomical coordinates, limited in capacity. Less is retained from complex images than simple images.
Silent substitution
If the action spectra of all photoreceptors types are known, spatial or temporal stimulus patterns can be designed which are invisible to some cone types while producing suprathreshold contrast for others. Thus one can study the range of psychophysical performance that is available for solely one type of cone signal.
Simple cells
One of three cell classifications for cells in the primary visual cortex (V1) proposed by Hubel & Wiesel. Simple cells show rectangular antagonistic on/off zones responding to bars of a particular orientations. They are described as a performing a linear filtering operation followed by a threshold nonlinearity. In a linear system the average response to a drifiting cosine grating will be a cosine at the same frequency. Because of the threshold, response to the negative half-cycles are suppressed.
Size constancy
Stabilized retinal images
Technique for examining perception without eye movement accompanied by loss of color and contour perception. Demonstrates that movement of an image across the retina is vital for perception.
Stereoscope
Device for creating a 3-D image of a drawn objects. Works by projects two different images of the objects to the eyes.
Stiles-Crawford effect
Light entering the eye through the center of the pupil is more effective than light entering at a peripheral point near the edge of the pupil. This is largely to to the directionally sensitive photoreceptors which are oriented towrad the center of the pupil. This helps to minimize the effect of stray light.
Stimulus equivalence
If the stimulus controlling behavior is a pattern of light on the retina than an infinite number of images are equivalent in their effects.
Superior colliculus
A nucleus in the midbrain that coordinate visual, somatic and auditory information adjusting movements of the head and eyes towards a stimulus. contains four types of maps, a visual map, a map of the body surface, a map for sound in space and a motor map. Receives inputs from the retina (via the optic tract), the visual cortex, the somatosensory system and auditory systems. Mediates saccadic eye movements. Is the source of two major descending tracts, the tectospinal tract and the tectopontine tract in addition to regions of the brain stem controlling eye movements.
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