Figure 4.

Disparity threshold and relative orientation. (A) Stereogram showing central target and surrounding reference grating patches. The disparity threshold was measured using a constant stimulus procedure to vary the phase disparity of the target, keeping the disparity of the reference grating at zero. (B) Target phase disparity at threshold. Means and standard errors for four observers for the five conditions of the experiment are shown from left to right: (1) target and reference vertically oriented (as in panel A); (2) target with no reference stimulus; (3) target oriented at 45°, reference at 90°; (4) target oriented at 45°, reference at 135°; and (5) target oriented at 45°, reference at 45°. Equivalent spatial disparities appear on the right ordinate. (Data from Farell, 2006.)