its ability to model overlapping actions. SGOMS SGOMS stands for Sociotechnical GOMS and was created to allow GOMS to model work in complex sociotechnical systems. GOMS is meant to model an individual user, working in isolation, with no unexpected interruptions, similar to a Cognitive Psychology experiment. This level of analysis is sometimes referred to as microcognition to distinguish it from macrocognition, which refers to real world cognition. SGOMS is meant to expand the applicability of GOMS to the macro cognitive level of analysis. To do this, SGOMS adds a high level control structure to GOMS, called the planning unit. This allows GOMS to deal with unexpected interruptions. A planning unit is a list of unit tasks. Planning units can be ordered (the unit tasks must be done in order) or situated (the unit tasks in the list are done as the situation demands). Consistent with CPM-GOMS, SGOMS assumes that the agent can monitor the situation in parallel in order to detect threats (neurophysiologically, this function is associated with the amygdala). Planning units can be interrupted and bookmarked so they can be resumed later. When a planning unit is interrupted the agent considers the situation and can resume the same planning unit or bookmark it and switch to a different planning unit. SGOMS does not prescribe how this choice is made but, if the decision is based on routine expertise, it can be included in the SGOMS model. Assumptions and errors Importance of assumptions in GOMS analysis Accurate assumptions are vital in GOMS analysis. Before applying the average times for detailed functions, it is very important that an experimenter make sure he or she has accounted for as many variables as possible by using assumptions. Experimenters should design their GOMS analysis for the users who will most likely be using the system which is being analyzed. Consider, for example, an experimenter wishes to determine how long it will take an F22 Raptor pilot to interact with an interface he or she has used for years. It can probably be assumed that the pilot has outstanding vision and is in good physical health. In addition, it can be assumed that the pilot can interact with the interface quickly because of the vast hours of simulation and previous use he or she has endured. All things considered, it is fair to use fastman times in this situation. Contrarily, consider an 80-year-old person with