Dual Mechanisms of Ion Absorption

A. W. Atkinson, B. E. S. Gunning, P. C. L. John, W. McCullough
1972 Science  
small (1.720) area subtended by the greatest extent of the test fields makes it unlikely that the results can be explained as being due to rod intrusion. The results I obtained when I increased the test-field luminance are contradictory to those expected for rod intrusion. Decreasing the background luminance by 0.5 log unit should decrease the latency differences if rod intrusion occurs, but it would not produce the 20-msec shift necessary to eliminate latency differences (13). Finally, subject
more » ... ). Finally, subject JA was tested for two trial sets with the background luminance raised 0.5 log unit above the test-field luminance. Again latency differences were eliminated, contrary to what would be expected from intrusion. In referring to the effects of wavelength on visual latency, no distinction has been made between effects of wavelength per se, that is, hue, and those of differences in saturation. Since only two wavelengths were used, 549 nm and 621 nm, and these are not of equal saturation, the importance of saturation cannot be evaluated on the basis of these experiments. The results of Vos and Walraven (5) and Walraven and Leebeek (6) indicate that relative visual latency is inversely proportional to the wavelength of light. Since the relationship between wavelength and saturation does not follow such a relationship, I think that the differences that are reported in this experi.ment are due primarily to hue and not to saturation. The discrepant results obtained with the various methods of measuring wavelength effects on visual latency (1-6) can be reconciled by my results. Visual latency differences related to the wavelength of light exist, but they cannot be demonstrated if luminance increments are present. Apparently the luminance cues take precedence because they have a shorter latency than chromatic cues.
doi:10.1126/science.176.4035.694 pmid:17778179 fatcat:rmpdbo6cmbfijej5yeolag2lum