Abstract
This study investigated the complex decisions made by engineers when conducting contaminated-land risk assessments. Experienced assessors studied summaries of site reports, which were composed of different combinations of relevant cues, and decided on the risk level of each site. Models from three theories of decision making were compared. Applying judgment analysis to develop a lens model provided the best account of the data, lending support to social judgment theory. A model based on a fast-and-frugal heuristic, the matching heuristic, did not fit the data as well; nor did a coherence model based on the theory of explanatory coherence. Comparison with decisions generated with the use of industry guidance showed only a moderate fit, suggesting that the standard procedure does not accurately represent how highly proficient domain practitioners make assessments in this context. Qualitative analyses of comments made by participants suggested that they used a combined approach that applied key cues as predicted by social judgment theory, integrated into a meaningful, coherent account, as predicted by the theory of explanatory coherence. Overall, these findings suggest a novel process in which a range of information is combined to form a coherent explanation of the data but in which key cues are more influential than others.