The document discusses using human logging to evaluate information visualization (infovis) systems. It describes logging insights, units of discovery, and "aha!" moments to gain a deeper understanding of how users interact with infovis systems compared to traditional system logging. The document also explores using physiological computing to capture additional metrics like eye tracking, heart rate, brain activity during interaction to provide new perspectives on cognitive load and insights. It acknowledges challenges in stimuli design, analysis, and validation when using these techniques.