Forward displacement in grasping and visually judging pliers

Abstract

Observers often tend to misremember the visual stopping point of a movement in the direction of movement (representational momentum). We investigated whether this forward displacement also occurs in grasping. We asked participants to close virtual pliers after the pliers had been opening or closing. The participants' thumbs and index fingers were attached to robot arms which allowed us to provide haptic feedback about the location of the pliers' handles. In a visual task, participants judged the remembered final opening width of the pliers relative to a comparison stimulus. For grasping, we found forward displacement: participants opened their fingers wider if the pliers had been opening compared to when they had been closing. In contrast, we did not find clear forward displacement in the visual task. The effects in grasping and the visual task were not correlated between participants. These results seem to argue against the existence of one form of anticipation that serves both perception and grasping.