Underestimation of large distances in active and passive locomotion.

Our ability to estimate distances, be it verbally or by locomotion, is exquisite at close range (action space). At distances above 100 m (vista space), verbal estimates continue to be quite accurate, whereas locomotor estimates have been found to be grossly underestimated. Until now, however, the latter have been performed on a treadmill, which might not translate to real-world walking. We investigated if the motor underestimation found on the treadmill holds up in a natural environment. Observers viewed pictures of objects at distances between 10 and 245 m and were asked to reproduce these distances in a blindfolded walking task (using passive movement or an active production method). Active and passive locomotor judgments underestimated far distances above 100 m. We conclude that underestimation of large distances does not depend on the medium (treadmill vs. real-world) but rather on the sensory modality and effort involved in the task.