Gauging the utility of ambient displays by measuring cognitive load

Ambient Displays, a sub-class of ubiquitous computing, aim to present non-critical information using peripheral visualisation with minimal distraction. The utility of Ambient Displays relies on providing useful, well-designed information in a way that does not increase the users cognitive load. Assessing the cognitive load of an Ambient Display is thus an important part of the development process. In this paper we review the key design dimensions of Ambient Displays and consider how they impact on cognitive load. We then examine various approaches for measuring cognitive load before describing a study that investigates a novel use of a dual-task measure to evaluate the cognitive load of a specific Ambient Display. A between-subjects design with 40 participants was used, with the Ambient Display active for half of these participants. All participants completed three different primary tasks (n-back, visual digit span, and auditory digit span) alongside the secondary, Detection Response Task. The results show that the n-back task is the most appropriate for manipulating primary task load when evaluating such displays and that the dual-task paradigm can be used to provide an objective measure of workload. Analysis of the participants primary and secondary task performance indicates that the evaluated Ambient Display imposed no additional cognitive load.