Virtual and augmented reality headsets are unique as they have access to our facial area, an area that presents an excellent opportunity for always-available input and insight into the user's state. Their position on the face makes it possible to capture bio-signals as well as facial expressions.  The  PhysioHMD platform introduces a software and hardware modular interface built for collecting affect and physiological data from users wearing a head-mounted display. The platform enables researchers and developers to aggregate and interpret signals in real-time and use them to develop novel, personalized interactions, as well as evaluate virtual experiences. Our design offers seamless integration with standard HMDs, requiring minimal setup effort for developers and those with less experience using game engines. The PhysioHMD platform is a flexible architecture that offers an interface that is not only easy to extend but also complemented by a suite of tools for testing and analysis. We hope that PhysioHMD can become a universal, publicly available testbed for VR and AR researchers.

To create a seamless experience, we have integrated several bio-signal sensors into the faceplate of an HTC VIVE VR headset and utilized the Shimmer3 sensor for emotion-sensing. For the collection of Galvanic Skin Response, dry electrodes were positioned on the forehead area due to the fact that it is one of the areas most dense with sweat glands. GSR data reflects emotional arousal, but in order to identify how arousal, valence, motivation, and cognition interact in response to physical or psychological stimuli, it becomes necessary to complement GSR with other biosensors. For the heart rate, a PPG (photoplethysmogram) sensor, which senses the rate of blood flow by utilizing light to monitor the heart’s pumping action, was placed in the temple region of the user. This is done to get insights into the respondent's physical state, anxiety and stress levels (arousal), and to determine how changes in their physiological state relate to their actions and decisions.