An ACT-R Modeling Framework for Interleaving Templates of Human Behavior

An ACT-R Modeling Framework for Interleaving Templates of Human Behavior Michael Matessa (mmatessa@arc.nasa.gov) NASA Ames Research Center, Mail Stop 262-4 Moffett Field, CA 94035 USA work has been done in modeling multi-tasking in the ACT-R architecture (Byrne & Anderson, 2001; Lee & Taatgen, 2002; Salvucci, 2002). This paper presents a new framework, ACT-Stitch, which combines the usefulness of modeling at the task level with the process theory of a lower-level cognitive architecture. It uses a process of macro-compilation similar to that used by Salvucci and Lee (2003) to translate CPM-GOMS templates into ACT-R productions. Their system will be compared to the current system in the discussion section, but one difference is that their system models at the level of KLM- GOMS, which does not interleave cognitive operators (John & Kieras, 1996). The control structure used by ACT-Stitch to achieve the interleaving of cognitive operators from different templates is one of the major contributions of this paper. The research involved in producing ACT-Stitch will benefit reusable template research by showing what aspects of template and interleaving theory are important in a new architecture that processes resource information. ACT-R research will benefit from re-usable productions packaged at a higher task level and from the multi-tasking control structure used that allows ACT-R to interleave productions from different templates. Abstract Performance modeling has been made easier by architectures which package psychological theory for reuse at different levels. Both CPM-GOMS, which packages theory at the task level, and ACT-R, which packages theory at the lower level of rules for perceptual-motor interaction, have been shown to be useful. This paper describes ACT-Stitch, a framework for translating CPM-GOMS templates and interleaving theory into ACT-R. The research involved in producing ACT-Stitch will benefit reusable template research by showing how to implement templates and interleaving in a new architecture that processes resource information. ACT-R research will benefit from re-usable productions packaged at a higher task level and from the multi-tasking control structure used that allows ACT-R to interleave productions from different templates. The zero-parameter predictions of ACT-Stitch are empirically validated. Introduction Predicting well-practiced human performance in human- computer interaction (HCI) domains by means of computer modeling is a valuable but difficult process. For example, modeling has been used to predict the outcome of a test of new computer workstations, saving a telephone company millions of dollars per year (Gray, John & Atwood, 1993), but much of the modeling was done by hand. For accurate predictions, a large amount of psychological theory needs to be applied. Several modeling architectures have been developed to make modeling easier by packaging this theory for reuse. CPM-GOMS (John, 1988; 1990) uses templates of behavior to package at a task level (e.g., mouse move-click, typing) predictions of lower-level cognitive, perceptual, and motor resource use. These templates are interleaved to reflect the ability of skilled people to perform parts of one task in parallel with another. For example, an eye-movement study has demonstrated interleaving in a hand-washing task -- while people perform the subtask of first getting their hands wet they interleave a look to the soap dispenser before performing the motor actions in the subtask of soaping their hands (Pelz & Canosa, 2001). The CPM-GOMS theory has been automated (John, et al., 2002) in a computational architecture that schedules blocks of abstract resource use (Freed et al., 2003). ACT-R (Anderson & Lebiere, 1998; Anderson et al., submitted) uses a computational production system architecture for packaging knowledge at the lower level of rules for working with cognitive and perceptual information and motor actions. In contrast with CPM-GOMS, the ACT-R system can interact with an environment to perceive objects and manipulate them. However, ACT-R does not have a built-in theory of multi-tasking which would interleave tasks, although some Templates Templates are building blocks of human behavior containing a detailed theory of cognitive, perceptual, and motor behaviors. They are beneficial for modelers because they package this theory at the task level and can be reused in different applications (Matessa et al., 2002). Even behavior as simple as a mouse move and click requires coordination of the use of cognitive, perceptual, and motor resources, as Figure 1 shows in PERT chart form with boxes representing resource use and lines indicating dependencies. The template was developed for the simple task of clicking on lit circles by Gray and Boehm-Davis (2000), but has been successfully reused for clicking to operate a simulated automated teller machine (John, et al., 2002). Templates require a theory of interleaving to reflect the ability of skilled people to perform operations from different tasks in parallel. When CPM-GOMS was first developed, this interleaving was done by hand, with modelers applying their knowledge of the psychology involved. John et al. (2002) codified this knowledge and implemented automated interleaving in a system that scheduled blocks of abstract resource use. Results from this work were used in the construction of ACT-Stitch templates that produce productions which ACT-R can interleave.