Debating Affective and Emotional Brain–Computer Interfaces (BCIs): When Will Online Affective BCI Truly Be Realized and Benefit Patients

This study critically examines the scientific foundations and application prospects of affective and emotional brain–computer interfaces (BCIs), with particular attention to the feasibility of online affective BCIs in clinical and practical contexts. The paper first delineates the conceptual boundaries between emotion and affect, highlighting their interrelations and distinctions. It then reviews recent advances in multimodal signal acquisition, emotion induction paradigms, and decoding algorithms, while analyzing key challenges such as signal–label alignment, the trade-off between real-time performance and robustness, and ethical as well as academic boundaries. The discussion underscores that the inherent subjectivity of emotions and the instability of their recognition remain major theoretical and technical barriers to large-scale implementation. The study concludes by calling for a cautious and scientifically rigorous approach to future development, ensuring that progress in this emerging field is both responsible and sustainable.