Scaling up from Micro Cognition to Macro Cognition: Using SGOMS to build Macro Cognitive Models of Sociotechnical Work in ACT-R

Scaling up from Micro Cognition to Macro Cognition: Using SGOMS to build Macro Cognitive Models of Sociotechnical Work in ACT-R Robert L. West (Robert_west@carleton.ca) Institute of Cognitive Science, 1125 Colonel By Drive Ottawa, ON K1S 5B6 Canada Sterling Somers (sterling@sterlingsomers.com) Institute of Cognitive Science, 1125 Colonel By Drive Ottawa, ON K1S 5B6 Canada Abstract SGOMS is a way of scaling up GOMS models to model multi agent work in complex sociotechnical systems. In particular, it allows GOMS to handle interruptions, multi-tasking, and re-planning. West and Pronovost (2009) discussed some of the theoretical issues around building an SGOMS model in ACT-R. This paper presents work in progress for two such models. Specifically, we used ACT-R to create a model of a worker in a sandwich shop and a model of a commercial airline pilot. Problems with scaling ACT-R up to the macro cognitive level are discussed and solutions are presented. Keywords: ACT-R, GOMS, microcognition, macrocognition, sociotechnical systems, cognitive modeling. As Simon (1962) pointed out in his story about the two watchmakers, when a system gets more complex it is more likely to be organized in a hierarchical way, especially if the system has to exist in a noisy environment. In the story, two watchmakers make identical watches but one goes out of business will the other one flourishes. The unsuccessful watchmaker does not have a hierarchical approach to making watches. Instead he makes a watch in one go, but if he is interrupted it all falls apart. The successful watchmaker makes various parts of the watch separately, and then assembles them together into higher-level parts, which are then assembled into even higher-level parts, and so on until the watch is made. If he is interrupted only the part he is working on falls apart. Because the watches are popular there are many calls to order them and therefore many interruptions, which are catastrophic for the first watchmaker but manageable for the second watchmaker. SGOMS is a theory of Macro Cognition that is based on this idea. The argument behind SGOMS is that cognitive modeling designed to work at the level of psychology experiments (micro cognition) can scale up to higher-level tasks where interruptions are common, if additional hierarchical structure is added. If the system is truly hierarchical then the micro cognitive processes should not change when macro level processes are needed for a task. SGOMS is a theory about what sort of macro level processes need to be added. Specifically, SGOMS is a theory of what needs to be added to GOMS modeling (Card et al., 1983). GOMS is based on the theory that all expert routine behaviors and cognitions can be explained using a limited set of control structures. These are: Goals, Operators, Methods, and Selection-Rules (implemented as Production Rules). In addition GOMS assumes that these elements are organized as Unit Tasks (Newell, 1990). Unit Tasks are a means of partitioning a task to avoid overloading the cognitive system (i.e., taking in information too fast) and downtime (i.e., taking in information too slowly). GOMS works well for modeling isolated, individual tasks. However, GOMS does not work well in environments where interruptions, multi tasking, and teamwork are common (West & Nagy, 2007). Simon’s (1962) story suggests that this is due to insufficient hierarchical structure. SGOMS augments GOMS by adding additional structure to allow the productive use of GOMS in complex sociotechnical environments. To accomplish this, SGOMS adds a higher-level control structure and introduces an additional constraint on unit tasks related to this structure. In addition to avoiding overload and downtime, unit tasks must also be small enough to avoid most interruptions (West & Nagy, 2007). By adding this constraint unit tasks become islands of work that will likely be completed without interruption and where normal GOMS modeling can be applied. In SGOMS, control of the unit tasks is accomplished by planning units. Planning units are higher-level representations of the work that specify how to use unit tasks to accomplish a particular part of the task. In our experience so far, planning units can often be represented as a list of unit tasks. Planning units can be interrupted, bookmarked, and restarted; therefore planning units provide a cognitive mechanism to deal with task interruptions and multi-tasking. West and Provnost (2009) characterized sociotechnical systems as having a tension between sticking to an existing plan and adapting to unforeseen local circumstances. Sociotechnical systems require that workers act in a coordinated way and this frequently involves having a plan. Planning meetings and briefing sessions are common in the sociotechnical workplace. However, it is often the case that workers have to adapt to or work around events or circumstances that were unforeseen in the plan. According to SGOMS theory, when a worker is interrupted and cannot