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.