No transfer from visual to visuomotor perceptual learning and vice versa

Perceptual learning is usually very specific. For example, performance improves when observers train with a vertical bisection stimulus. However, this improvement does not transfer to a horizontal bisection stimulus. Here, we show that perceptual learning is even specific for the response mode. Observers trained with vertical bisection stimuli comprising two outer and a central line. In the visuomotor learning condition, observers could adjust the center line by means of a computer mouse. Observers placed the center line in the middle between the two outer lines with a small displacement towards either the left or right outer line indicated by a cue randomly chosen. We asked observers to adjust the smallest displacement they could perceive. In the classical, visual learning condition, observers indicated by push button press if the center line was closer to the left or right outer line. Performance improved strongly in both conditions. However, improvements in either condition did not transfer to the other condition as shown by pre- and post-measurements, i.e., visuomotor learning did not improve visual performance and visual learning did not improve visuomotor performance. Hence, perceptual learning is specific to the response mode used during training- even though the visual stimuli are almost identical.