Authentic cases (for example, determining the best way to spend $100 for a week’s worth of groceries) are better than concrete cases (calculating how much rocket fuel is needed to get a two-ton payload into space),and concrete cases are better than symbolic cases (manipulating the variables in the equation f = ma). Regardless of the kind of case that is selected,beginning instruction should start with a case that is more generic or prototypical in nature to foster near transfer, but then should shift to cases that are more unusual to promote far transfer (Butterfield & Nelson, 1989).Cases that illustrate early learning skills should use simple simulations, and cases that illustrate advanced skills should use complex simulations (Bjork, 1994; Mayer & Sims, 1994).