This paper is in two parts: I, a brief description of the identity theory of the development of the object concept and a computational model that describes the three stages of that theory and, II, the running of that model on two experiments important in the analysis of developnent of the object concept. Th emodel is designed to help determine which parameters in the development process might best explain changes whithin the object comprehension skills of infants. The discussion presents a set of perceptual invariants that can be used: a), to describe changes between developmental stages and, b) offer the potential for a cost/gain metric foor that development. The model is written in PROLOG, a very gigh level computer language. Detailed descriptions of PROLOG (6)(15) and further uses of PROLOG to model provlem solving skills (7) may be found elsewhere