The Cost of Virtuality Switching: Searching for Physical and Virtual Targets in Optical-See-Through Augmented Reality

As AR applications expand across our daily lives, understanding user interactions within mixed environments-where virtual and physical objects coexist-has become increasingly important. This work investigates human performance and behavior during visual search and selection tasks across three object conditions: (1) virtual objects only, (2) physical objects only, and (3) a combination of virtual and physical objects (Mixed) requiring frequent virtuality switching. We also vary the distance to the target plane while maintaining subtended visual angle: a ‘near’ condition at the headset's focal plane and a ‘far’ condition at a mid-zone action space distance of 3 meters. Results indicate that, while there are some small effects that can be linked back to established display phenomena such as Vergence-Accommodation Conflict, a main cause for performance differences among the object conditions comes from people adjusting their search and selection behavior to the challenges of virtuality switching, resulting in Mixed conditions requiring significant longer completion times, associated with significantly larger head motion, eye movement, and controller movement. Mixed conditions also resulted in significantly lower accuracy for target selection. Virtual-to-Physical transitions took the longest to complete, followed by Physical-to-Virtual transitions, both significantly longer than transitions to targets within the same virtuality. Participants also reported increased Eye Strain, Fatigue, and Task Load with the Mixed conditions. This work provides insight into the complexities of mixed object interaction and presents quantitative assessments of pronounced virtuality switching, with implications for designing effective AR interfaces.