Volume 23, Issue 12, 1983, Pages 1533–1538

Discrimination of moving gratings at and above detection threshold

  • Department of Psychology, University of York, York , YO1 5DD,England

Abstract

Two experiments examined the discriminability of moving gratings. Experiment 1 measured the difference between detection and discrimination thresholds for gratings of equal spatial frequency drifting in the same direction at different rates. It was found that, as Watson and Robson [Vision Res.21, 1115–1122 (1981)] had found with counterphase modulated gratings, only very coarse discriminations could be made. The results suggest that just two labelled channels can account for the velocity discrimination of gratings at detection threshold. The second experiment investigated the discriminability of suprathreshold moving gratings. These results also support the idea that rate of movement is mediated by two broadly tuned channels.

These data were first reported to the Association for Research in Vision and Ophthalmology, Sarasota, 1982 (Thompson, 1982b).