The influence of environmental and body-based action constraints on distance judgments

To determine action capabilities, an actor must take into account environmental features and the actor's individual body and capabilities. Previous research has shown that changing an actor's ability to reach by changing the body influences judgments of distance to reachable objects. The current studies tested whether both environmental and body constraints that limit reaching would influence judged distances to reachable objects. In Experiment 1, participants estimated distances to a small object when it was both in front of and behind a clear, reach-limiting Plexiglas barrier. Participants estimated their ability to reach the object (yes or no response), and then visually matched the distance from the edge of the table to the object with a tape measure. Participants judged the distance to the object as farther when the object was behind the barrier than when it was in front of the barrier; the barrier also reduced estimates of reach ability. In Experiment 2 participants estimated distances in front of and behind a barrier while their dominant or non-dominant hand was weighted, a body constraint on action. Distances within reachable space were judged to be significantly farther than the other conditions when the target was behind the barrier and the dominant (reaching) hand was weighted. This study suggests that action-relevant environmental constraints do influence judgment of distances and interact with body-based constraints.