Underlying humanity’s social abilities is the brain’s capacity to interpersonally synchronize. Experimental, lab-based neuropsychological studies have demonstrated that inter-brain synchrony can be technologically mediated. However, knowledge in deploying these technologies in-the-wild and studying their user experience, an area HCI excels in, is lacking. With advances in mobile brain sensing and stimulation, we identify an opportunity for HCI to investigate the in-the-wild augmentation of inter-brain synchrony. We designed “PsiNet,” the first wearable brain-to-brain system aimed at augmenting inter-brain synchrony in-the-wild. Participant interviews illustrated three themes that describe the user experience of modulated inter-brain synchrony: hyper-awareness; relational interaction; and the dissolution of self. We contribute these three themes to assist HCI theorists’ discussions of inter-brain synchrony experiences. We also present three practical design tactics for HCI practitioners designing inter-brain synchrony, and hope that our work guides a HCI future of brain-to-brain experiences which fosters human connection.

Sleep plays a paramount role in maintaining healthy bodily functioning. Yet, poor sleep is an increasingly prevalent global health concern. Most current sleep technology tracks sleep, but how to design for promoting sleep is relatively underexplored. We highlight the potential of employing closed-loop systems for promoting sleep onset and explore this through the design and study of “Dozer”, a closed-loop beanie that accelerates sleep onset through auditory and electrical brain stimulation after detecting drowsiness in EEG. In an in-the-wild study, participant interviews revealed three UX themes (closed-loop neurocentric agency, awareness of hardware, and awareness of feedback), which ultimately suggested that participants fell asleep in spite of Dozer, rather than through its assistance. We interpret these results and provide actionable design tactics to inform the design of closed-loop sleep systems moving forward. We hope this work gives rise to a deeper understanding of designing closed techno-physiological loops.