This study purported to reconsider the role of top-down processing in Cubist paintings. We especially examined the role that Pablo Picasso’s drawings of human body proportions played in his Cubist experimentation. The diagram for the theory of human proportion is an intellectual tool traditionally used in drawing to provide a geometric basis for observation. It serves as a kind of internal model for top-down processing and also as a reference for modifying bottom-up information, to make it conform to an ideal figure or typical image. After clarifying the theoretical scope of this diagram, this study analyzed the drawings of human body proportions made by Pablo Picasso in 1907, and its creative application to Cubist works. Picasso’s use of the diagram of proportion not only disrupts traditional bottom-up information processing, but also problematizes traditional top-down information processing. The final section of this paper further discusses how such problematization of top-down processing is tied to Cubism’s question regarding the perception of reality. In doing so, we reconsider the ways in which abstract schemes that appear in Cubist works create a new dialogue with the sense of reality in a relativist instead of universalist manner.