論文アブストラクト：360° videos are made using omnidirectional cameras that capture a sphere around the camera. Viewers get an immersive experience by freely changing their field of view around the sphere. The problem is that current interfaces are designed for a single user, and we do not know what challenges groups of people will have when viewing these videos together. We report on the findings of a study where 16 pairs of participants watched 360° videos together in a "guided tour" scenario. Our findings indicate that while participants enjoyed the ability to view the scene independently, this caused challenges establishing joint references, leading to breakdowns in conversation. We conclude by discussing how gaze awareness widgets and gesturing mechanisms may support smoother collaborative interaction around collaborative viewing of 360° videos.