“…User State. The sensors that could be integrated within future HMDs would empower an AR system to have a rich, instant understanding of user's state, such as activities (IMU [86,219], camera [80,128,194,201], microphone [103,218,229,230]), cognitive load (eye tracking [71,104,238], EEG [20,224]), attention (eye tracking [56,99,204,231], IMU [123], EEG [213]), emotion (facial tracking [233,236], EEG [202,216]) and potential intent (the fusion of multiple sensors and low-level intelligence [14,111,211]). Depending on a user's state, the design of explanations could be different.…”