The influence of stimulus length on the oblique effect of contrast sensitivity.

Contrast sensitivity for grating of different orientations was measured at various stimulus lengths. The oblique effect of contrast sensitivity was observed to increase in magnitude as the length of the truncated gratings was increased from 0.5 to 5.6 deg. This finding refutes a purported distinction between the contrast sensitivity oblique effect and the orientation discrimination oblique effect. Thus, these results are consistent with the idea that the contrast sensitivity oblique effect and the orientation discrimination oblique effect share the same common underlying anisotropic basis. These results also show that grating summation differs at oblique and nonoblique orientations in terms of length summation as well as in terms of width summation.