The researchers reported that their first cycle described the development of the concept of chance measurement whereas their second cycle represented consolidation of the concept (in terms of using ratio concepts) and application of it to more complex problem solving contexts. Watson and her colleagues have also investigated other probability constructs such as luck (Watson, Collis, & Moritz, 1995) and fairness (Watson & Moritz, 2003b). Similar to Jones et al. (1997), the models they constructed for these latter constructs include only one U-M-R cycle. As researchers continue to build and refine models of development in probabilistic thinking they should remain alert to the possibility of multiple learning cycles within a particular mode of operation. In addition, more research is needed to investigate the formal mode of reasoning about probability.