The spillover effects of fairness events in competitive sports events on audience social trust: a quasi natural experimental analysis.

Introduction: How fairness incidents in sports events cross the boundary of entertainment and spill over onto spectators' social trust has been a continuing controversy in existing research. This paper proposes the framework of "surrogate institutional signals," which treats the arena, with its explicit rules, public enforcement, and verifiable outcomes, as a low cost diagnostic window on which spectators perform Bayesian updating. Methods: Merging CFPS and CGSS microdata with Weibo and Zhihu text streams and embedded trust game experiments, the study screens 486 candidate incidents by independent double coding into a database of 63 fairness incidents covering 2018 to the first half of 2025, distinguishes the incidents into regulative, procedural, and substantive types, and measures trust as a ladder of six tiers ordered by institutional distance from the focal incident. Identification combines the Callaway-Sant'Anna staggered difference-in-differences weighted by attention with synthetic control, and adds competing mediation and causal forest analysis. Results: The core results show that the absolute value of the negative spillover effect of procedural incidents on social trust is 3.29 times that of regulative incidents and 1.88 times that of substantive incidents; the effect attenuates monotonically along the trust ladder, from -0.612 for the officiating crew and organizing committee to -0.221 for public institutions outside sport, or 36.1% of the innermost effect, and to -0.129 for generalized trust in strangers, while close ties show no detectable change and 67.0% of the outside sport effect survives conditioning on dissatisfaction with the incident; the surrogate institutional signal pathway carries 51.3% of the spillover effect, while moral shock and media accessibility contribute 28.4 and 20.3% respectively, and the three pathways display the temporal evolution of "emotion first, cognition takes over"; conditional average treatment effects are significantly heterogeneous, with the subgroup high in both political interest and media use responding most strongly. Discussion: The study identifies a bounded and graded rather than a diffuse spillover, delimits the reach of trust updating across domains, and provides actionable mechanistic evidence for event governance and information disclosure.