Proceedings of the Annual Meeting of the Cognitive Science Society

This paper compares the Act-R and Soar cognitive architectures, focusing on their theories of control. Act-R treats control (conflict resolution) as an automatic process, whereas Soar treats it as a potentially deliberate, knowledge-based process. The comparison reveals that Soar can model extremely flexible control, but has difficulty accounting for probabilistic operator selection and the independent effects of history and distance to goal on the likelihood of selecting an operator. In contrast, Act-R's control is well supported by empirical data, but has difficulty modeling task-switching, multiple interleaved tasks, and dynamic abandoning of subgoals. The comparison also reveals that many of the justifications for each architecture's control structure, such as some forms of flexible control and satisficing, are just as easily handled by both.