Abstract

Test and field sensitivity data suggest that small, brief, foveal lights are detected by red/green pathways whose spectral tuning functions broaden with decreases in stimulus size and duration. Data also show that spectral tuning depends, not on the absolute size of test or field, but on the spatial relation between the two.¹ This study reports a similar finding in the temporal domain. Flashed-field sensitivities are measured for a brief test on a brief field (40 ms each); long-duration test on a long-duration field (500 ms each); and a brief test on a long-duration field (40 ms on 500 ms); SOA = 0. Test wavelength is 580 nm. Test diameter is 11′, field diameter, 49′. Both lights are presented on a 4.0 log td steady white adapting background. The field sensitivity in the brief test/long duration field condition resembles the red/green function. The field sensitivities broaden when test and field are the same duration (40 or 500 ms). The results are analogous to those obtained by varying the relative size of test and field. With a small test and large field, the field sensitivity looks red/green. With the two lights the same size, the data are unimodal. The findings suggest that a change in spectral sensitivity can signify a change in the spectral tuning of a single opponent pathway.

© 1986 Optical Society of America