Recently we and others reported significantly less location specificity in motion direction learning than that reported in previous classical studies. The classical studies performed motion direction training with a special format of the method of constant stimuli, in that it contained a single level of direction difference defined by a pair of fixed stimuli. In contrast we and others used staircase methods that varied the direction difference trial by trial. We suspect that multiple sessions of practice with a single direction difference could allow an observer to take advantage of some subtle local cues for direction discrimination. Such local cues may be unavailable at a new stimulus location, which causes learning to be more location specific. To test this hypothesis, we jittered slightly the directions of a stimulus pair by the same amount while keeping the direction difference constant, so as to disturb the potential local cues. As a result we observed significantly more transfer of learning to untrained locations. The local cue effects may also explain the recent controversies regarding the finding that foveal motion direction learning becomes significantly more transferrable to a new direction with TPE (training-plus-exposure) training. One specific study by Zili Liu and collaborators that challenges the transfer finding also used a single-level direction difference for training. We first replicated their results. But we found that if the directions of the stimulus pair that defined the direction difference were again jittered while the direction difference was kept constant, motion direction learning transferred significantly more to an orthogonal direction with TPE training. Our results thus demonstrate the importance of using appropriate psychophysical methods in training to reduce local-cue related specificity in perceptual learning.

Xiong, Y.Z., Xie, X.Y., & Yu, C*. (2015). Location and direction specificity in motion direction learning associated with training with a single-level method of constant stimuli.  Vision Research , in press.