Strategic competence is one of the many critical components necessary for students to be successful in mathematics. Broadly, strategic competence is the ability to "formulate mathematical problems, represent them, and solve them" (National Research Council, 2001, p. 124). This involves both the knowledge of strategies including representations that may be used to solve a problem and the ability to effectively and efficiently use strategies while flexibly switching between strategies in response to the demands of a problem situation (National Research Council, 2001). Central to strategic competence are representations. While there are various definitions of a representation (e.g., Goldin, 2003; Kaput, 1987; Pimm, 1995), for this study, a representation is considered to be "a combination of something written on paper, something existing in the form of physical objects and a carefully constructed arrangement of idea in one's mind" (Davis, Young, & McLaughlin, 1982, as cited in Smith, 2003, p. 266). Clearly, many different representational forms (e.g., mental image, written language, oral language, action movements, symbols, manipulatives) exist (Zawojewski & Lesh, 2003). A critical idea about representations, however, is that they are not static end products but rather tools for cognitive activity (Pape & Tchoshanov, 2001). As the Principles and Standards for School Mathematics (National Council of Teachers of Mathematics [NCTM], 2000) noted, a representation refers "both to process and to product. .. to the act of capturing a mathematical concept or relationship in some form and to the form itself" (p. 67). Therefore, when viewed as a tool of cognitive activity for solving mathematical problems, representations can be used for analyzing problems and planning solutions, justifying and explaining actions, predicting consequences, monitoring and evaluating progress, and integrating and communicating results in forms that are useful to others (Pape & Tchoshanov, 2001). Diagrams and Mathematical Word Problem Solving Although all representational systems are important for developing mathematical understanding (Owens & Clements, 1998; Pape & Tchoshanov, 2001; Presmeg, 1986) and various representational systems can be used to solve word problems, the focus of this study is specifically on self-generated diagrams. According to Diezmann and English (2001), a 438558L DQ36310.