Interpersonal synchronization as an objective measure of listening engagement

Listening engagement plays a crucial role in effective communication and knowledge transfer, reflecting a state of deep absorption in an auditory stimulus. The available behavioral assessments of listening engagement are limited in capturing its multidimensional nature. Measuring listening engagement objectively using brain and body signals is a compelling alternative. In particular, interpersonal synchronization--observed through synchronized neural and physiological responses among listeners--may offer a promising objective measure. In this study, we examined synchronization of brain activity, heart rate, and electrodermal activity between participants while they listened to engaging and non-engaging stories. Subjective engagement ratings were collected as a ground truth reference. Results showed higher interpersonal synchronization across all modalities when participants listened to engaging stories compared to non-engaging ones, with significant correlations between synchronization measures and ratings of subjective engagement. These results confirm that synchronization may be a reliable, objective marker of listening engagement. We anticipate that these results will provide a powerful framework for future research in relevant domains, including auditory neuroscience, education, and communication science, and enable impactful real-world applications, such as automatically tracking audience engagement in education, entertainment, and broader societal contexts.