The reversible limbs of a stick walker

A stick walker whose limbs consisted of segments reversible in depth was presented from the frontal perspective. As one would expect, in the upright orientation observers were more likely to see the arms bend forwards and the legs bend backwards with respect to the body. In the inverted orientation, however, observers were more likely to see all limbs bend in the same direction rather than in random directions, so that the arms and the legs appeared to be either concave or convex structures at any given time. This codirectional perception of limb structure in the inverted orientation suggests that inverted body parts are organised on the basis of their perceptual similarities, including figural and dynamic features, rather than stored representations of the human body form, leading to the usual perception of upright walkers.