The SYNCON project aims to investigate the role of interpersonal neural synchrony (INS) in verbal conversations. INS is the coupling of brain oscillations between two interlocutors and is thought to support conversation patterns such as turn-taking and phonetic convergence. However, previous studies have limitations in testing the role of INS in free-flowing conversations, as they were either conducted in a non-ecologically valid context or the evidence was purely correlational. The SYNCON project seeks to overcome these limitations by using EEG hyperscanning with multi-person brain stimulation (tACS) and personalized neuroscience. The project will first measure the correlation between INS and mutually engaged conversations, characterized by enhanced turn-taking and phonetic convergence. This measurement will yield a dyad-specific INS profile, considering properties such as frequency, phase, and topography. In a second experiment utilizing a longitudinal design, these profiles will be used to exogenously induce INS between interlocutors and promote mutually engaged conversations. Understanding the causal role of INS in conversations has potential applications in facilitating interpersonal communication in therapeutical and educational contexts. This project will address critical gaps in our understanding of the neural underpinnings of human communication and its potential use in applied contexts.