Visual learning in the hyperacuity range in adults.

We investigated the amount, speed, and specificity of the learning of new visual tasks in adult humans using stereoscopic depth perception and vernier discrimination as the sensitive probes for learning. The results of psychophysical experiments in untrained adult observers indicate two phases of highly specific perceptual learning in humans: a fast phase and a slower one. Both types of learning might take place relatively "early" during pattern recognition in the visual cortex, since learning was very specific, without transfer between different stimulus orientations.