The Presenccia project takes an operational approach to the concept of presence. Presenccia's approach lets the project team assess the extent of presence using tools beyond traditional questionnaires, and therefore avoid many of the problems involved with sole reliance on these. Instead, the team considers the extent to which mixed reality and VR participants realistically respond to virtually generated sensory data. Specifically, they measure the similarity of their response with what they might observe or predict if the sensory data—the situation, place, or events—were real, rather than virtual. This article describes the project's research highlights.