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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(More)
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 one's 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(More)
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(More)
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(More)
Postcompletion errors, which are omissions of actions required after the completion of a task's main goal, occur in a variety of everyday procedural tasks. Previous research has demonstrated the difficulty of reducing their frequency by means other than redesigning the task structure [Byrne, M. Task structure and postcompletion error in the execution of a(More)
In the United States, computer-based voting machines are rapidly replacing other older technologies. While there is potential for this to be a usability improvement, particularly in terms of accessibility, the only way it is possible to know if usability has improved is to have baseline data on the usability of traditional technologies. We report an(More)
In the 2006 U.S. election, it was estimated that over 66 million people would be voting on direct recording electronic (DRE) systems in 34% of the nation's counties [8]. Although these computer-based voting systems have been widely adopted, they have not been empirically proven to be more usable than their predecessors. The series of studies reported here(More)
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(More)
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(More)