Proceedings of the Annual Meeting of the Cognitive Science Society

ive reasoning and problem solving is error-prone. One such pattern is manifested in that people err more often when problems are indeterminate than when problems are determinate W e suggest that an incomplete problem representation could account for the observed pattern of errors. W e further contend that in verbal reasoning such incomplete representation stems from a lack of systematic representations of connectives (e.g., and, or, if, etc.), and, therefore, extemalization of relations denoted by sentential connectives should improve people's representations of multiple possibilities. These predictions were tested in three reported experiments. Results indicate that determinate problems were easier to represent and recall than indeterminate problems. Furthermore, there was a tendency to represent and recall indeterminate problems as if they were determinate ones by fruncating the number of possibilities compatible with the problem. Finally, external aids dramatically improved representation and recall of indeterminate problems. These results are discussed in relation to theories of representation and reasoning.