Bimanual interference associated with handling different tool transformations

Research on bimanual coordination of hand movements has identified several loci of bimanual interference, including interference because of programming different movement parameters or selecting different targets for the two hands. This study investigates the extent and origin of interference when participants execute bimanual actions with tools. In the experiments, participants moved two tools, one with each hand, to two directly cued target locations. One type of tool transformed the body movement into a spatially compatible movement of the effective part of the tool, whereas the other transformed it into a spatially incompatible movement. Tool transformations for the two hands were either the same or different. Furthermore, target locations were either in the same or in different spatial directions. Results indicated significantly shorter reaction times (RTs) and less errors when tool transformations were the same for both hands. In addition, movements were initiated more quickly and less error-prone when targets were in the same direction, but this effect was modulated by the congruency of the two lever transformations. Investigations of the time course of the effects revealed that they were not because of early perceptual processing (Experiment 2). Furthermore, the general pattern of results occurred for different grip positions (Experiment 3) and different lever types (Experiment 4), suggesting that it reflects rather general constraints in bimanual coordination of tool-use actions.