The Red-Line of Workload: Theory, Research, and Design

Multi-tasking is now ubiquitous component of our lives; despite the fact that we all can cite an incident where multi-tasking put us in a difficult situation. The reason so many of us do multi-task is that most of the time we are capable of effective dual task performance. Hart and Wickens (2008) have defined the point where one traverses safe and effective multi-tasking to dangerous and ineffective multi-tasking as the “red-line” of workload. In this panel, we will discuss this “red-line” of workload from the theoretical, empirical, and practical viewpoints. To that end, we first examine what theories of attention can help guide empiric search for this red line and where these theories must be expanded with further research. The greatest need is research that will allow human factors practitioners to identify the red line of workload before a system has been developed. One approach to achieving this research is to leverage the approach of industrial ergonomics, which has successfully defined physical workload limits by using data from safety incidents. Another avenue of research to be discussed is that which will lead to refinement of our theories and understanding of cognitive function to improve our ability to predict the red line. Next we move to the problem of evaluating systems to ensure that the red line of workload is not crossed. In particular, we will discuss the possibility of using task analysis, specifically, CPM-GOMS to predict if a system design will lead to excessive workload. Finally, we present two system design strategies for maintaining a cognitive workload that is below the red-line. The first of these is an adaptive automation using eye-tracking to reduce screen clutter when it appears workload has become so high an error may occur. The second design strategy presents four research based design principles for reducing workload to acceptable levels.