Michael D. Byrne

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.

ACT-R/PM and menu selection

Understanding the interaction of a user with a designed device such as a GUI requires clear understanding of three components: the cognitive, perceptual and motor capabilities of the user, the task to be accomplished and the artefact used to accomplish the task. Computational modeling systems which enable serious consideration of all these constraints have only recently begun to emerge. One such system is ACT-R/PM, which is described in detail. ACT-R/PM is a production system architecture that has been augmented with a set of perceptual-motor modules designed to enable the detailed modeling of interactive tasks. Nilsens (1991) random menu selection task serves two goals: to illustrate the promise of this system and to help further our understanding of the processes underlying menu selection and visual search. Nilsens original study, two earlier models of the task, and recent eye-tracking data are all considered. Drawing from the best properties of the previous models considered and guided by information from the eye-tracking experiment, a series of new models of random menu selection were constructed using ACT-R/PM. The final model provides a zero-parameter fit to the data that does an excellent, though not perfect, job of capturing the data.

A Working Memory Model of a Common Procedural Error

Systematic errors In performance are an important aspect of human behavior that have not received adequate explanation. One such systematic error is termed postcompletion error; a typical example is leaving ones card In the automatic teller after withdrawing cash. This type of error seems to occur when people have an extra step to perform in a procedure after the main goal has been satisfied. The fact that people frequently make this type of error, but do not make this error every time, may best be explained by considering the working memory load at the time the step is to be performed: The error is made when the load on working memory is high, but will not be made when the load is low. A model of performance In the task was constructed using Just and Carpenters (1992) CAPS that predicted that high working memory load should be associated with postcompletion errors. Two experiments confirmed that such errors can be produced in a laboratory as well as a naturalistic setting, and that the conditions under which the CAPS model makes the error are consistent with the conditions under which the errors occur in the laboratory.

The tangled Web we wove: a taskonomy of WWW use

A prerequisite to the effective design of user interfaces is anunderstanding of the tasks for which that interface will actuallybe used. Surprisingly little task analysis has appeared for one ofthe most discussed and fastest-growing computer applications,browsing the World-Wide Web (WWW). Based on naturally-collectedverbal protocol data, we present a taxonomy of tasks undertaken onthe WWW. The data reveal that several previous claims aboutbrowsing behavior are questionable, and suggests that thatwidget-centered approaches to interface design and evaluation maybe incomplete with respect to good user interfaces for the Web.

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.

Serial modules in parallel: The psychological refractory period and perfect time-sharing

The authors describe ACT-R/perceptual-motor (ACT-R/PM), an integrated theory of cognition, perception, and action that consists of the ACT-R production system and a set of perceptual-motor modules. Each module (including cognition) is essentially serial, but modules run in parallel with one another. ACT-R/PM can model simple dual tasks such as the psychological refractory period (PRP), including subtle results previously explained with executive process interactive control (EPIC, D. E. Meyer & D. E. Kieras, 1997a). The central difference between the theories is that EPICs productions can fire in parallel, whereas in ACT-R/PM, they are serial. Results from three PRP-like experiments with more demanding cognitive requirements indicate that cognitive processing for the 2 tasks need not overlap. ACT-Rs activation-based retrieval processes are critical in accounting for the timing of these tasks and for explaining the dual-task performance decrement.

Evaluating animations as student aids in learning computer algorithms

Abstract We conducted two experiments designed to examine whether animations of algorithms would help students learn the algorithms more effectively. Across the two studies we used two different algorithms — depth-first search and binomial heaps — and used two different subject populations — students with little or no computer science background and students who were computer science majors — and examined whether animations helped students acquire procedural and conceptual knowledge about the algorithms. The results suggest that one way animations may aid learning of procedural knowledge is by encouraging learners to predict the algorithms behavior. However, such a learning improvement was also found when learners made predictions of an algorithms behavior from static diagrams. This suggests that prediction, rather than animation per se, may have been the key factor in aiding learning in the present studies. These initial experiments served to highlight a number of methodological issues that need to be systematically addressed in future experiments in order to fully test the relationship between animation and prediction as well as to examine other possible benefits of animations on learning.

Using icons to find documents: simplicity is critical

A common task at almost any computer interface is that of searching for documents, which GUIs typically represent with icons. Oddly, little research has been done on the processes underlying icon search. This paper outlines the factors involved in icon search and proposes a model of the process. An experiment was conducted which suggests that the proposed model is sound, and that the most important factor in searching for files is the type of icons used. In general, simple icons (those discriminable based on a few features) seem to help users, while complex icons are no better than simple rectangles.

Learning to achieve perfect, timesharing: Architectural implications of Hazeltine, Teague, and Ivry (2002)

E. Hazeltine, D. Teague, and R. B. Ivry have presented data that have been interpreted as evidence against a central bottleneck. This article describes simulations of their Experiments 1 and 4 in the ACT-R cognitive architecture, which does possess a central bottleneck in production execution. The simulation model is capable of accounting for the emergence of near-perfect timesharing in Experiment 1 and the detailed data on the distribution of response times from Experiment 4. With practice, the central bottleneck in ACT-R will be reduced to a maximum of 50 ms (1 production cycle) and can often be much less, depending on timing of stages and variability in their times. The authors also show, with a mathematical analysis of E. Hazeltine et al.s Experiment 2, that the expected dual costs for these kinds of highly practiced tasks will be small in many circumstances, often under 10 ms.

Effects of scent and breadth on use of site-specific search on e-commerce Web sites

Users faced with Web sites containing many possibly relevant pages often have a decision to make about navigation: use the menu of links or use the provided site search function. Two studies were conducted to examine what users do when faced with this decision on e-commerce Web sites, and how users go about deciding which method to attempt. An exploratory study revealed a wide distribution of searching and browsing behavior across sites and users. Counter to some predictions, use of the site search functions did not yield faster or more accurate performance in locating products. Questionnaire data suggested that factors relevant to the menu structure, interface element prominence, information scent and user dispositions all influenced the decision of whether to browse or search a site for a product. A second experiment utilizing novel e-commerce sites and allowing for more control of factors found to be important in the first study found that browsing behavior was influenced by both the breadth and information scent of the menus. These results suggest that providing site search should not be used to compensate for poor menu design, and provide further evidence regarding the design of effective menu structures.