Tool use influences perceived shape and perceived parallelism, which serve as indirect measures of perceived distance.

Targets presented just beyond arm's reach look closer when observers intend to touch them with a reach-extending tool rather than without the tool. This finding is one of several that suggest that a person's ability to act influences perceived distance to objects. However, some critics have argued that apparent action effects were actually due to effects on the judgments rather than on the perception. In other words, the target does not actually look closer, but participants report that it is. To help counter this argument, the current experiments used an indirect measure of perceived distance: Participants reported perceived shape or perceived parallelism. The results revealed that triangles looked shorter and lines looked more horizontal to participants who reached with a tool, and therefore could reach the targets, than they did to participants who reached without the tool. These results demonstrate convergence across multiple types of judgments, a finding that undermines alternative, judgment-based accounts and suggests that the ability to reach an object changes the perceived distance to the object.