The Index of Cognitive Activity: measuring cognitive workload

The Index of Cognitive Activity is an innovative technique that provides an objective psychophysiological measurement of cognitive workload. As users operate in increasingly complex environments, it is essential that the designers of these environments understand the cognitive demands placed on the users. The Index of Cognitive Activity (ICA) provides an important estimate of the levels of cognitive effort of the user. The ICA is based on changes in pupil dilation that occur as a user interacts with a visual display. The Index is described, and several applications are presented.