This disclosure provides methods, devices, and systems for indicating an attentiveness of a user of a head-mounted display (HMD) device. The HMD device may include a camera configured to capture images of the surrounding environment, an electronic display configured to display the images captured by the camera, and one or more sensors configured to track a direction of gaze of the user. In some aspects, the HMD device may output an attention cue based on the images displayed on the electronic display and the user's direction of gaze. The attention cue may indicate an attentiveness of the user to a person or object in the surrounding environment. In some implementations, the attention cue may be output via an attention indicator disposed on an outer surface of the HMD device. In some other implementations, the attention cue may be output via a communication interface that communicates with another HMD device.