Covert visual attention is a subtle part of human vision that has been widely researched in the psychology community. Most often visual attention is thought to involve movements of the eyes or head; however, covert visual attention does not involve overt movements of any sort. It has often been described in an homuncular sense as the "mind's eye." This paper introduces both a new model of covert visual attention and a new approach in which to investigate attention. The approach is based on five assertions: (1) Development of models of attentional processes should occur in the context of a fixed, explicit model of nonattentional processes. (2) Evaluation of attentional models should occur in the context of complete tasks. (3) Judgment of the quality of an attentional model should be with respect to its ability to cover many tasks while maintaining constant parameters. (4) Computer implementation and simulation of an attentional model and the tasks it claims to cover should be used for demonstrating its sufficiency. (5) A process model (a model that seeks to correspond at some level of analysis to actual mechanisms of behavior) should be able to account fw both the timing and the functions of behavior. N O V A (Not Overt Visual Attention), the first operator-based model of covert visual attention, is based on the Model Human Processor [Card, Moran, and Newell, 1983], a model of nonattentional processes that has been applied successfully in Human-Computer Interaction (HCI) research. In this paper w e review the results of using N O V A to model seven qualitatively different immediate-response tasks from the psychological literature. As a test of the sufficiency of N O V A , we implemented N O V A and each of the task models in the Soar cognitive architecture, a computer model of human behavior that has been proposed as the basis of Newell's "Unified Theories of Cognition" (UTC) [Newell, 1990]. N O V A is both a new theory of attention and a framework in which existing theories of attention have been unified.

John Laird came to UCSC in 1968, and graduated in 1972. In 1983, Laird was elected mayor of Santa Cruz, and became the first openly gay mayor in the United States. He was also a founding member of the Santa Cruz AIDS Project (SCAP). In 2002, Laird was elected to the California State Legislature as one of two of the first openly gay men to be elected to the Assembly. Laird was interviewed on September 13, 2001 in his office at the Santa Cruz County building. The timing of this interview was significant because it took place two days after the attacks on the World Trade Center on September 11, 2001.

PRIMs theory describes a computational foundation for un-derstanding task-general human learning and transfer usingrule-based cognitive architectures. Integration with ACT-Rhas yielded Actransfer, a model that replicates human learn-ing and transfer across many tasks. However, this model re-quires task-specific latency scaling parameters from ACT-Rto model different tasks, implying that there is missing com-putation in the theory. Neuroscience literature has separatelydefined the “task set” as the neural encoding that configuresstimulus-response rule behavior in working memory. The pro-cess of switching between different task sets is often used toexplain human latency costs. This paper introduces an alter-nate instantiation of PRIMs theory that enacts task set process-ing to account for the missing computation via a novel memorystructure called a procedure context. Human tasks of varyingcomplexity are modeled across two experiments. Procedurecontexts model human latencies and interference effects in alltasks by integrating latency, decision making, task representa-tion, and learning as aspects of a single unified process. Thisapproach offers promise for future modeling within cognitivescience by uniting theories from neuroscience and cognitivearchitectures.