What the researchers did amounts to real-life DVR. First they took a subject into a room with a video camera, had him put on a virtual reality headset, then asked hm to shake their head around to "try it out." While they were doing that, they switched to a recorded video, and the subject often wasn't the wiser--until the recording showed the subject himself walking into the room. They added one more layer after that: the researcher popped up on the end of the room to say it was all a just a recording. But (ha ha) that was a recording, too. Finally, the researcher revealed his live-and-in-person self.