What to do and how to do it: action representations in tool use.

Research on bimanual coordination has shown that the efficiency of programming an action is determined by the way the action is cognitively represented. In tool use, actions can be represented with respect to the spatial goal of the action (e.g., the nail that is to be hit by a hammer) or with respect to the tool and its transformation (i.e., the function that maps external target locations onto corresponding bodily movements). We investigated whether the way of cuing bimanual actions with tools affects their cognitive representation and the efficiency with which they are programmed. In one group of participants, tool transformations were specified by symbolic cues, whereas the targets were indicated by direct spatial cues. In another group of participants, symbolic cues specified the targets of the tool-use actions, whereas tool transformations were indicated by direct spatial cues. In a third group, both targets and tool transformations were cued directly by spatial cues. It was hypothesized that different cognitive representations would result in more or less efficient programming of the action. Results indicated longer reaction times and a higher error rate in the group with symbolic cuing of the targets as compared to the group with symbolic cuing of the transformations. The latter did not differ much from the direct cuing group. These results suggest that it is more efficient to represent bimanual tool-use actions in terms of the tool transformations involved than in terms of the targets at which they are directed.