When novices surpass experts: The difficulty of a task may increase with expertise.

A detailed look at the representations constructed by novice and expert computer programmers is presented. The issue is addressed by looking at the interaction between the representation naturally formed by programmers at each level of expertise and .an experimentally induced abstract or concrete mental set. The data suggest that, in the absence of an experimentally provided set, experts form abstract representations (denned here as what a program does), whereas novices form concrete representations (defined here as how a program functions). The data also suggest that appropriate sets can aid each group to form the representation not natural to them; however, these representations are not as stable as the preferred ones. The generality of the findings and the utility of the experts' representation of a task is discussed both in relation to computer programming and to problem solving in other domains. In the semantically rich domains of skilled problem solving (Bhaskar & Simon, 1977), the difference between experts and nonexperts is both qualitative and quantitative. Not only do experts perform better than novices on quantitative measures of skill but experimental manipulations also uncover qualitative differ- ences in the representations and strategies used by experts. Repeatedly, we find that the work- ing representations of experts are abstract conceptualizations of the original problem statement, whereas those of novices are less abstract and focus more on surface features of the problem. For example, in a recent ex- periment, Adelson (1981c) found that expert programmers used abstract, conceptually based representations when attempting to re- call programming material, whereas novices used syntactically based representations. Using a multitrial free-recall procedure, Adelson asked novice and expert programmers to recall a set of 16 lines of programming code that had been presented in random order. Although the subjects had not been told that the 16 lines