An Operator-Based Attentional Model of Rapid Visual Counting

In this paper we report on the use of our operatorbased model of human covert visual attention [Wiesmeyer and Laird, 1990] to account for reaction times in counting tasks in which a stimulus is presented and left undisturbed until a response is made. Previous explanations have not employed &n attentionally-driven model. Our model, which is based on the Model Human Processor [Card et a/., 1983], is an early selection model in which an attentional "zoom lens" [Eriksen and Yeh, 1985] operates under the control of cognition in order to both locate features in visual space and improve the quality of featural information delivered to short-term memory by perception. W e have implemented our model and the control structures to simulate rapid counting tasks in the Soar cognitive architecture [Laird et al., 1987], which has been suggested as the basis for a unified theory of cognition [Newell, 1990]. Reaction times in the counting task are explained using operator traces that correspond to sequences of deliberate acts having durations in the 50 msec range

An operator-based model of human covert visual attention.

Over the last thirty years there has been much research into the nature of covert visual attention, which is the portion of visual attention that does not involve movement of the head or eyes. Surprisingly, though the role of covert visual attention has been shown to be diverse, most attentional theories are not able to explain more than one observed behavior. For instance, a theory of how attention is involved in identification may not be able to explain how attention is involved in search. Of the theories that do attempt to explain more than one attentional phenomenon, there are few that are specified to the extent that they might be considered computational. I have developed an operator-based computational model of human covert visual attention in two dimensions that is based on the Model Human Processor. My theory, which is called "NOVA" (Not Overt Visual Attention), is unique because it accounts for behavior in seven of the most significant classes of visual attention experiments from the psychology literature. These include precuing, crowding, decay, illusory conjunctions, search, counting, and detection experiments. NOVA task models are composed of operator traces. Each operator trace is composed of a linear sequence of operators, which are deliberate acts, such as a shift of attention or an act of recognition. Timing calculations are made by summing durations of component operator applications, perceptual dependencies and motor actions. Task performance is explained by operator traces in all seven experiments, and in five of the seven experiments timing performance is explained. In the other two experiments, timing was not presented as part of the experimental results. Since operators apply in approximately 50 msec, that is the limit to the timing resolution of NOVA. I have implemented NOVA and all of my task models in the Soar cognitive architecture. Soar is well suited as a platform for implementing a model based on the Model Human Processor, since it possesses many of the Model Human Processor's most important aspects. Implementation is a check of NOVA's specification and evidence that NOVA could be integrated with more complex models of behavior.Ph.D.Computer Science and EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/103005/1/9227024.pdfDescription of 9227024.pdf : Restricted to UM users only

NOVA, Covert Attention Explored Through Unified Theories of Cognition

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