Is peripheral visual acuity susceptible to perceptual learning in the adult?

While it is generally accepted that foveal visual acuity in the adult has r eached an optimal value, claims for improvement of peripheral acuity with t raining in the adult persist in the literature. Practice effects in periphe ral hyperacuity have been amply documented. A carefully controlled test is here reported to examine the influence of training on the resolution thresh olds for two lines and on Landolt C acuity measurements in the retinal peri phery in eight normal adults. It involved 11-30 daily sessions of 300 respo nses with feedback. In some observers the first day's results were somewhat poorer, but otherwise the threshold curves were essential flat. Yet in the same location vernier acuity could be improved by 50%, in six training ses sions. Sustained and lasting neural modifications in peripheral vision can take place in stereoscopic, orientation, vernier, bisection and time discri minations, but not in resolution and Landolt C acuities. (C) 2000 Elsevier Science Ltd. All rights reserved.