The shape-weight illusion

Abstract

In the present experiment, we investigated the influence of the shape of 3-dimensional objects on haptic perception of weight. A systematic shape-weight illusion was found when subjects compared a tetrahedron to a cube: a cube was perceived as being heavier than a tetrahedron of the same physical mass and volume. However, when subjects compared a sphere to a tetrahedron or to a cube, some subjects perceived the sphere as heavier than the other objects, while other subjects perceived the sphere as being lighter. These results indicate that the influence of shape on haptic perception of weight is not mediated only by the perceived volume, as would be predicted from previous studies, but that some subject dependent factors are involved.