Orientation anisotropy: incidence and magnitude in Caucasian and Chinese subjects.

Cutoff spatial frequencies for sine-wave gratings were measured at four orientations for 100 Caucasian and 24 Chinese subjects, all of whom were raised in carpentered enviornments. For the Caucasian subjects, average acuity for horizontal and vertical gratings was superior to that for obliques by about one-quarter of an octive. However, about 10 percent of subjects showed an anisotropy of about one-eight of an ovtave. The carpentered enviornment explanation of orientation anisotropy cannot, in its present form, account for the wide variety of response patterns obtained, nor the differences between Chinese and Caucasian subjects.