He-lin Luo ¹ , Meng-fan Huang ¹ , Yu-hsin Kung ¹ , Shih-Yu Huang ¹ , Chia-wei Liang ² , Chih-Ming Kung ² and Yi-ping Hung ³ , ¹ Tainan National University of the Arts, Taiwan, ² Shih Chien University, Kaohsiung, Taiwan, ³ National Taiwan University, Taiwan

Emotional contagion refers to the psychological and behavioral phenomenon in which individuals unconsciously mimic the facial expressions, vocal patterns, postures, and movements of others during social interactions, resulting in corresponding changes in their own emotional states. With the rapid development of digital media and networked communication platforms, emotional transmission is no longer limited to face-to-face interaction, but increasingly mediated through multimodal digital signals such as symbolic icons, animated feedback, visual imagery, and auditory cues. This transformation has positioned emotional contagion as a critical research topic in the fields of Human-Computer Interaction (HCI) and Affective Computing.This study focuses on the transmission of positive emotions, specifically investigating the contagion effect of happiness through an interactive installation titled Quartic Smile. The system was designed to construct a real-time emotional feedback environment in which users can perceive and respond to the emotional expressions of others within a shared interactive space. By integrating real-time facial expression recognition, the system captures smiling behaviors as emotional triggers and translates them into visualized interactive responses, thereby facilitating emotional resonance and collective engagement among participants. To quantitatively evaluate the effectiveness of emotional contagion, two core metrics were defined in this study. The first is the contagion level, which is calculated based on the frequency of smiles and reflects the intensity and distribution of emotional transmission among users. The second is the contagion speed, measured by the cumulative duration of smiling behaviors between participants, representing the temporal dynamics and responsiveness of emotional propagation. The experimental results indicate that Quartic Smile effectively enhances positive emotional interaction and demonstrates the potential of real-time interactive systems to shape collective emotional atmospheres and social engagement patterns. This study is based on research and data from 2017, which have been reorganized and revised.

Smile Detection, Emotion Recognition, Real-Time System, Public Interactive Installation