Inferring Causal History froms Shape

The shape of an object often seems to tell us something about the object's history; that is, the processes of growth, pushing, stretching, resistance, indentation, and so on, that formed the object. A theory is offered here of how people are able to infer the causal history of natural objects such as clouds, tumors, embryos, leaves, geological formations, and the like. Two inference problems are examined: the first is the inference of causal history from a single shape. It is claimed that this inference consists of two simple and yet powerful rules, based upon the symmetry and curvature structure of the shapes. When these two rules are applied to a large collection of shapes, it is found that the resulting causal histories accord remarkably well with intuition. The second inference problem is the recovery of intervening causal history between two successive shapes that are known to be two stages in the development of the same object. This type of inference is manifested, for example, when a doctor compares two X‐rays, taken a month apart, of the same tumor, and is able to conjecture the intervening growth. It is found that a grammar of only six operations is sufficient to generate the later shape from the earlier one via psychologically meaningful process‐extrapolations. Finally, a basic heuristic by which human beings seem to infer complex temporal relations between different processes in the past is proposed, and investigated in detail.