(1) Detection thresholds at 10 Hz and high grating contrasts were approximately 11-15 arcsec in the fovea and 37-47 arcsec at 30 degrees eccentricity.
(2) These results suggest that in the absence of other clinical findings to the contrary, the demonstration of gross stereopsis with either the Frisby (730 arcsec) or Lang (733 or 800 arcsec) test in the preschool child implies normal binocular function.
(3) The threshold luminance contrast difference required to produce a just detectable change in spatial position corresponds to a spatial shift of 5-20 arcsec in the centroid of the retinal light distribution, depending upon contrast relative to the background.
(4) Increasing the intensity of the perturbating line (to equal that of the outer lines) elevated thresholds for small separations (less than 4 arcmin) to approximately 6 arcsec but had no effect on the threshold for larger separations.
(5) In the second experiment, preschool children with abnormal binocular vision were tested with the Lang and Frisby stereotests to determine if large disparities (730 to 800 seconds of arc [arcsec]) could be passed without normal binocular vision.
(6) With a stationary stimulus, observers can detect a vernier cue of less than 10 arcsec and acuity is unaffected by retinal-image motion of up to 3 deg s-1 We confirm this finding, but provide evidence against any general deblurring mechanism by showing that another kind of hyperacuity, discrimination of the distance between two parallel lines (spatial interval acuity), is interfered with by motion.