Theory Revision and Redescription Complementary Processes in Knowledge Acquisition James A. Dixon 1 and Elizabeth Kelley 2 1 University of Connecticut and 2 Queen’s University, Kingston, Ontario, Canada ABSTRACT—Children acquire complex relational repre- sentations of the world. Explaining the acquisition of these representations has been a significant challenge for theo- ries of cognitive development. Recent work suggests that two processes, theory revision and redescription, operate in an iterative, complementary fashion to produce new representations. Given a novel situation, children use theory revision to generate a candidate relational struc- ture and can modify that structure in response to error. Redescription detects regularities created through suc- cessful use of that structure in interaction with the envi- ronment; these regularities are consolidated into new representations, which are then available to the theory- revision process. The complementary nature of these processes is illustrated by recent work on representational change in a gear-system task and in arithmetic concepts. Theory revision and redescription occupy different, but mutually supportive, niches in knowledge acquisition. KEYWORDS—knowledge acquisition; relations; representa- tion; cognitive development Children appear to rapidly and effortlessly develop an under- standing of the complex relational structures in their physical and social environments. For example, children acquire an understanding of the properties of objects, such as the simple fact that one object can physically support another (Casasola, 2005). Likewise, they understand properties of social systems, such as popularity in their peer group (Cillessen & Rose, 2005). Researchers in cognitive development have long recognized that children must possess powerful mechanisms for acquiring new representations in order to develop such a rich understanding of the world. Delineating the mechanisms of representational change has been an important and long-standing challenge for researchers working in the Genevan tradition, grounded in the work of Piaget and his colleagues (e.g., Karmiloff-Smith & In- helder, 1974; Piaget, 1954), as well as the mainstream cognitive tradition (e.g., Case & Okamoto, 1996; Siegler & Araya, 2005). Much of this work on children’s cognitive development has focused on how children generate hypotheses and test them against external evidence, a process we refer to as theory revi- sion. A smaller body of research has focused on how represen- tations self-modify as a result of their own activity, a process we call redescription. These two processes, theory revision and redescription, although not the only identified mechanisms of representational change, appear to be central to knowledge acquisition. Moreover, recent research shows that these two pro- cesses iteratively build on one another, thereby driving the development of knowledge structures. Here we review work demonstrating this complementary relationship. THEORY REVISION AND REDESCRIPTION Theory Revision Previous research suggests that the process of representational change is akin to theory revision (e.g., Halford, Brown, & Thompson, 1986; Kuhn, Garcia-Mila, Zohar, & Andersen, 1995). When a child encounters a novel object or situation, he or she proposes a relational structure among its constituent parts. As the child interacts with the new object or situation, evidence accumulates regarding the adequacy of the hypothesized rela- tional structure. If the hypothesized structure fails to predict the properties of the new object or situation (i.e., generates errors), the child will refine the hypothesis or perhaps propose a com- pletely new one. For example, Halford et al. (1986) gave children information about a block’s width, depth, and height and asked them to predict whether it would sink or float. Children proposed initial hypotheses and adjusted those hypotheses based on feedback about the flotation of individual blocks. This process Address correspondence to James A. Dixon, Department of Psy- chology, 406 Babbidge Road, Unit 1020, University of Connecticut, Storrs, CT 06269-1020; e-mail: james.dixon@uconn.edu. CURRENT DIRECTIONS IN PSYCHOLOGICAL SCIENCE Volume 16—Number 2 111 Copyright r 2007 Association for Psychological Science