Signal Decentralization of Agenda-Setting Power and Domain-Selective Bridging: Algorithm Design Beyond the Echo Chamber Debate

Summary

Masahiro Fujita published a paper on arXiv (cs.CY) on August 5, 2026, arguing that echo chambers are an inevitable consequence of human cognition evolutionarily designed to prioritize high-relevance information at small-group scale combined with engagement-optimizing algorithms, making conventional prescriptions demanding individual behavioral change of low feasibility. The paper constructs an Agenda Democratization Index (ADI) quantifying decentralization of agenda-setting power using four variables — barrier to entry, granularity, interactivity, and feedback resolution — and a Social Information Health (SIH) model integrating ADI with bridging mechanism strength. Based on this model, the author proposes domain-selective bridging, incorporating bridging alongside engagement into algorithmic scoring functions, optimizing bridging weight per information domain based on variability and collective scope. An agent-based simulation comparing no bridging, uniform bridging, and domain-selective bridging designs demonstrated that domain-selective bridging substantially outperforms uniform bridging on a joint efficiency measure, improving information sharing in domains relevant to collective decision-making while maintaining user experience in hobby and lifestyle domains. The paper reframes the echo chamber debate from a normative opposition over elimination to an engineering design problem of which domains, to what degree, and through what algorithm design bridging should be implemented.