Scott Douglass

An integrated theory of the mind.

Adaptive control of thought-rational (ACT-R; J. R. Anderson & C. Lebiere, 1998) has evolved into a theory that consists of multiple modules but also explains how these modules are integrated to produce coherent cognition. The perceptual-motor modules, the goal module, and the declarative memory module are presented as examples of specialized systems in ACT-R. These modules are associated with distinct cortical regions. These modules place chunks in buffers where they can be detected by a production system that responds to patterns of information in the buffers. At any point in time, a single production rule is selected to respond to the current pattern. Subsymbolic processes serve to guide the selection of rules to fire as well as the internal operations of some modules. Much of learning involves tuning of these subsymbolic processes. A number of simple and complex empirical examples are described to illustrate how these modules function singly and in concert.

Eye tracking the visual search of click-down menus

Click-down (or pull-down) menus have long been a key componentof graphical user interfaces, yet we know surprisingly little abouthow users actually interact with such menus. Nilsens [8] study onmenu selection has led to the development of a number of models ofhow users perform the task [6, 21. However, the validity of thesemodels has not been empirically assessed with respect to eyemovements (though [l] presents some interesting data that bear onthese models). The present study is an attempt to provide data thatcan help refine our understanding of how users interact with suchmenus.

Practice and Retention: A Unifying Analysis

What is the strength of a memory trace that has received various practices at times tj in the past? The strength accumulation equation proposes the following: strength = sigma tj-d, where the summation is over the practices of the trace. This equation predicts both the power law of practice and the power law of retention. This article reports the fits of the predictions of this equation to 5 experiments. Across these experiments, participants received as many as 240 trials of practice distributed over intervals as long as 400 days. The experiments also varied whether participants were just practicing retrieving an item or practicing applying a relatively complex rule. A model based on this equation successfully fit all the data when it was assumed that the passage of psychological time slowed after the experimental session. The strength accumulation equation was compared with other conceptions of the retention function and the relationship of the retention function to the practice function.

Tower of Hanoi: evidence for the cost of goal retrieval.

Past research on the Tower of Hanoi problem has provided clear evidence for the importance of goal-subgoal structures in problem solving. However, the nature of the traditional Tower of Hanoi problem makes it impossible to determine whether there is any special cost associated with storing or retrieving goals. A variation of the Tower of Hanoi problem is described that allows one to determine separately if there is an effect of how long a goal has to be retained on storage time or how long ago it was formed on retrieval time. This paradigm provides evidence for an effect of retention interval on retrieval time and not on storage time. An ACT-R (Adaptive Control of Thought-Rational) simulation of these data is described, which treats goal memory as no different from other memories.

Eye Movements Do Not Reflect Retrieval Processes: Limits of the Eye-Mind Hypothesis

This research investigated whether eye movements are informative about retrieval processes. Participants learned facts about persons and locations, and the number of facts (fan) learned about each person and location was manipulated. During a subsequent recognition test, participants made more gazes to high-fan facts than to low-fan facts, and gazes to high-fan facts had a longer duration than gazes to low-fan facts. However, there was no relation between the order in which items were fixated and the relative effect of person or location fan. The effect of person and location fan on gaze duration also did not differ with whether it was the person or location being fixated. A model assuming that the process of retrieval is independent of eye movements was successfully fit to the data on the distribution of gaze durations. According to this model, the effect of fan on number of gazes and gaze duration is an artifact of the longer retrieval times for high-fan facts.

Broader Bandwidth in Student Modeling: What if ITS were EyeTS?

The ability of an ITS to develop an accurate student model is inherently limited by the bandwidth of information available. We have completed an exploratory research project showing that eye movement data provide a means of broadening this bandwidth. This paper describes three examples in which more information about cognitive process is available from having access to a students eye movements than is available simply from key presses and mouse clicks.

Characteristics of fluent skills in a complex, dynamic problem-solving task.

We examined critical characteristics of fluent cognitive skills, using the Georgia Tech Aegis Simulation Program, a tactical decision-making computer game that simulates tasks of an anti-air-warfare coordinator. To characterize learning, we adopted the unit-task analysis framework, in which a task is decomposed into several unit tasks that are further decomposed into functional-level subtasks. Our results showed that learning at a global level could be decomposed into learning smaller component tasks. Further, most learning was associated with a reduction in cognitive processes, in which people make inferences from the currently available information. Eye-movement data also revealed that the time spent on task-irrelevant regions of the display decreased more than did the time spent on task-relevant regions. In sum, although fluency in dynamic, complex problem solving was achieved by attaining efficiency in perceptual, motor, and cognitive processes, the magnitude of the gains depended on the preexisting fluency of the component skills. These results imply that a training program should decompose a task into its component skills and emphasize those components with which trainees have relatively little prior experience. Actual or potential applications of this research include learning and training of complex tasks as well as evaluation of performance on those tasks.

Eye-Movements during Unit-Task Execution in a Complex Problem-Solving Situation

We have studied the performance of subjects as they acquired skill in the Georgia Tech Aegis Simulation Program (GT-ASP) with a particular focus on their eye movements. Our task analysis showed that the GT-ASP breaks down into the selection of unit tasks and the execution of these unit tasks. We focused on the Identification unit-task. Our results showed that most of the practice benefit in Identification came from increasing efficiency during cognitive process, in which people make inferences and decisions on the basis of the currently available information. We also analyzed eye fixations when people perform this unit-task. Participants showed different fixation patterns, depending on what portion of the unit-task was being executed. Fluency in a dynamic complex problem-solving seems to be achieved by efficiency in cognitive as well as perceptual processes.