Practice effects on the use of visual and haptic cues during grasping

Mapping of arbitrary color cues onto object properties such as mass can influence the control of fingertip forces. One can view the development of that mapping as a motor learning issue, and its development should therefore be influenced by practice schedule. During an acquisition phase, 24 participants lifted color-cued objects that differed in mass. The masses were presented in either blocked or random orders. A test phase consisted of lifts of a midmass object; on some lifts, the object's mass was unexpectedly changed. The change was either accurately color cued or miscued. Only blocked practice led to visually mediated scaling of fingertip forces to object mass. During the test phase, previous blocked practice resulted in reliance on visual cues, and random practice led to a reliance on haptics (sense of touch). Those findings suggest that the integration of arbitrary color cues and haptic information is dependent on practice conditions.