Representational momentum in perception and grasping: translating versus transforming objects.

Representational momentum is the tendency to misremember the stopping point of a moving object as further forward in the direction of movement. Results of several studies suggest that this effect is typical for changes in position (e.g., translation) and not for changes in object shape (transformation). Additionally, the effect seems to be stronger in motor tasks than in perceptual tasks. Here, participants judged the final distance between two spheres after this distance had been increasing or decreasing. The spheres were two separately translating objects or were connected to form a single transforming object (a dumbbell). Participants also performed a motor task in which they grasped virtual versions of the final objects. We found representational momentum for the visual judgment task for both stimulus types. As predicted, it was stronger for the spheres than for the dumbbells. In contrast, for grasping, only the dumbbells produced representational momentum (larger maximum grip aperture when the dumbbells had been growing compared to when they had been shrinking). Because type of stimulus change had these different effects on representational momentum for perception and action, we conclude that different sources of information are used in the two tasks or that they are governed by different mechanisms.