Abstract
Different geometries are used to model perceived psychological space. Affine geometry is one such model which can be used to understand how we map physical space to perceived space. In such affine transformations, properties like coplanarity of points, parallelism of a pair of lines and ratio of lengths of line segments in the same direction, remain invariant. One approach to study such a visual space is to consider its intrinsic structure, that is, how the spatial judgments that people make, relate to each other. According to action-specific approach to perception, perceived distance to targets is scaled by effort required to walk that extent. In this experiment, we tested whether effort required to walk affected the intrinsic structure of perceived space, by using Varignon’s theorem. According to Varignon’s theorem, if we join the bisection points of the four edges of an arbitrary quadrilateral, it forms a parallelogram in affine space. Also, bisection points of the line joining bisections of opposite edges will coincide with each other in the case of an intrinsically consistent affine structure. Here, for half of the participants, we manipulated their effort required to walk, by using a treadmill. The participants were shown two adjacent vertices of a quadrilateral in each trial and were asked to blind-walk to the midpoint. They also performed bisection judgments of the bisections of opposite edges in the last two trials and we checked the distance between these two final points for intrinsic consistency. Although we did not find a significant effect of required effort on the intrinsic consistency of perceived affine space, we observed a trend that there was more distortion when effort required to walk was manipulated using a treadmill. The results suggest that perceived space might be affected by effort required to act on physical space.