Hastening orientation sensitivity.

Previous perceptual learning studies have shown that sensitivity to subtle orientation differences improves with practice at oblique axes but not with practice at cardinal axes. The cause of this anisotropy in angular resolution is uncertain, and it is not known whether the same anisotropy pertains to temporal resolution-the minimum stimulus duration needed to achieve a specified angular resolution. Here, we investigated the hypothesis that cardinal improvements were previously absent because long stimulus durations yielded maximal precision, even at the start of training.