This paper reports on a laboratory study which compared conceptual data models developed by casual autonomous users using the relational and the extended entity relationship (EER) representation techniques. It was found that the EER model led to better user performance in modeling binary relationships, while the relational model was better in modeling unary relationships. Subjects found it difficult to model ternary relationships using either model, although the performance using the EER model was slightly better. In general, there was evidence that the EER model led to better user performance. Subjects using the EER model were more confident about their solutions and perceived the model as easier to use than their relational counterparts. The study's results raise questions concerning user performance using the relational model for a discovery (conceptual modeling) task.