Temporal-discontinuity detection with contrast-modulated gratings.
Three experiments on temporal-discontinuity detection were carried out. In experiment 1, temporal-discontinuity thresholds were measured for sinusoidal gratings by the use of the double-staircase method. A sinusoidal grating was presented twice successively. The subject judged whether or not an interval was present. The temporal-discontinuity threshold increased as the spatial frequency of the grating increased, but decreased as the contrast of the grating increased. In experiment 2, contrast-modulated gratings were used instead of the sinusoidal grating. The temporal-discontinuity threshold increased as the carrier frequency increased, and the threshold for each contrast-modulated grating was similar to that for the no-modulation (sinusoidal) grating whose contrast was the same as the maximum local contrast of the contrast-modulated grating. In experiment 3, temporal-discontinuity thresholds were measured for low-contrast (3%) sinusoidal gratings. The thresholds were very low, even for such low-contrast gratings. These results suggest that the low-spatial-frequency channels are not involved in detecting the modulation frequency of the contrast-modulated grating. Rather, the local contrast seems to be the determinant of the detection of the contrast-modulated grating itself.
Ichihara
S
S
Department of Psychology, Tokyo Metropolitan University, Japan.
Susami
K
K
D001288:Attention; D015350:Contrast Sensitivity; D005260:Female; D005425:Flicker Fusion; D006801:Humans; D008297:Male; D010364:Pattern Recognition, Visual; D010470:Perceptual Masking; D011601:Psychophysics; D012684:Sensory Thresholds