Tool use and perceived distance: when unreachable becomes spontaneously reachable.

An interesting issue about human tool use is whether people spontaneously and implicitly intend to use an available tool to perform an action that would be impossible without it. Recent research indicates that targets presented just beyond arm's reach are perceived closer when people intend to reach them with a tool rather than without it. An intriguing issue is whether this effect also occurs when people are not explicitly instructed to use a tool to reach targets. To address this issue, we asked participants to estimate distances that were beyond arm's reach in three conditions. Participants who held passively a long baton underestimated the distances as compared to participants with no baton (Experiment 1). To examine whether this effect resulted from holding the baton, we asked participants to estimate distances while holding passively a shorter baton (Experiment 2). We found that holding this short baton did not influence distance perception. Our findings demonstrate that when people aim at performing a task beyond their action capabilities, they spontaneously and implicitly intend to use a tool if it substantially extends their action capabilities. These findings provide interesting insights into the understanding of the link between the emergence of tool use, intention, and perception.