Testing a counter-intuitive prediction of optimal cue combination

Weighted averaging is said to be optimal when the weights assigned to the cues minimize the variance of the final estimate. Since the variance of this optimal percept only depends on the variances of the individual cues, irrespective of their values, judgments about a cue conflict stimulus should have the same variance as ones about a cue consistent stimulus. We tested this counter-intuitive prediction with a slant matching experiment using monocular and binocular slant cues. We found that the slant was indeed matched with about the same variance when the cues indicated slants that differed by 15 degrees as when they indicated the same slant.