Abstract
Through instruction from others and direct experience with the goal-directed manipulation, people establish typical patterns of tool use. In this study, participants performed horizontal or vertical motions in one of two tool-holding conditions: empty hands or holding tools. Tools were selected that are more typically moved either horizontally or vertically. In both tool-holding conditions, participants were required to make movements in time with videos of another person moving along the same or the orthogonal axis. Videotaped actions contained tool and empty hand motions. We measured the interference on motions produced (as in Kilner, Paulignan, & Blakemore, 2003) to determine to what extent hand and tool motions elicit covert imitation from participants making motions in the same or different tool-holding condition and with the same or different tool type. Our results first indicate that variance in individual observed motions affects variance produced motions. Additionally, the relationship between the orientation of the longer axis of a hand or object one is moving and the orientation of the longer axis of an observed hand or object seems to affect interference. Finally, our results suggest that prior combinations of a tool-holding/tool-type conditions may affect interference in subsequent condition combinations.