Walkable distances are bioenergetically scaled.

In perceiving spatial layout, the angular units of visual information are transformed into linear units appropriate for specifying size and extent. This derivation of linear units from angular ones requires geometry and a ruler. Numerous studies suggest that the requisite perceptual rulers are derived from the observer's body. In the case of walkable extents, it has been proposed that people scale distances to the bioenergetic resources required to traverse the extents relative to the bioenergetic resources currently available. The current study sought to rigorously test this proposal. Using methods from exercise physiology, a host of physiological measures were recorded as participants engaged in exercise on 2 occasions: once while provided with a carbohydrate supplement and once with a placebo. Distance estimates were made before and after exercise on both occasions. As in previous studies, the carbohydrate manipulation caused decreased distance estimates relative to the placebo condition. More importantly, individual differences in physiological measures that are associated with physical fitness predicted distance estimates both before and after the experimental manipulations. Results suggest that walkable distances are bioenergetically scaled.