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Abstract

Two recent experiments contributing to the analysis of temporal resolution in human foveal vision are reviewed.

First, the critical duration for the detection of a single line on a bright ground is determined. When the line is brighter than the ground, critical duration amounts to 4·10 −3 s as opposed to 12·10 ‒3 s when the line is darker than the ground. This difference is discussed in connection with ON- and OFF- centre retinal ganglion cells in primates. Relations to possible physiological substrates of feature binding are sketched.

Second, apparent motion generated by successive onset of two adjacent lines on a bright ground is studied. Psychophysical thresholds for the detection of temporal order of the onset of two dark lines are determined for different distances of the lines. The minimum of the distance function found is very narrow centering around 3 \ This is small compared to the distance function measured in earlier experiments and when the lines are brighter than the background. This difference indicates that the signals of ON- and OFF- centre ganglion cells are processed separately in the perception of local motion. Findings and conclusions are discussed with respect to earlier anatomical and physiological findings in the visual cortex of primates.