Two experiments were conducted to determine the extent to which perceptual
learning transfers between orientation and direction discrimination. Naive
observers were trained to discriminate orientation differences between two
single-line stimuli, and direction differences between two single-moving-do
t stimuli. In the first experiment, observers practiced the orientation and
direction tasks along orthogonal axes in the fronto-parallel plane. In the
second experiment, a different group of observers practiced both tasks alo
ng a single axis. Perceptual learning was observed on both tasks in both ex
periments. Under the same-axis condition, the observers' orientation sensit
ivity was found to be significantly elevated after the direction training,
indicating a transfer of learning from direction to orientation. There was
no evidence of transfer in any other cases tested. In addition, the rate of
learning on the orientation task was much higher than the rate on the dire
ction task. The implications of these findings on the neural mechanisms sub
serving orientation and direction discrimination are discussed. (C) 1999 El
sevier Science Ltd. All rights reserved.