“…With a few exceptions (e.g., Baroody, Ginsburg, & Waxman, 1983; Canobi, in press; Canobi et al, 1998, 2002; Hsieh & Baroody, 2000; Langford, 1981), children's knowledge of each addition principle has been examined separately, making it difficult to assess changes in the interrelations among them and, ipso facto, conceptual development (Bisanz & Lefevre, 1992). Indeed, although Resnick (1986) argued that commutativity and associativity are not distinct in children's understanding but arise from knowledge of additive composition, other researchers have argued that children acquire an understanding of commutativity prior to an understanding of associativity (Close & Murtagh, 1986; Langford, 1981). Therefore, further research into the comparative difficulty of recognizing different kinds of principle-based relations between addition problems is needed.…”