Ephemeral connections, persistent effects: Cooperation dynamics in temporal networks with historical interactions

Digital technologies enable seamless and frequent ephemeral network connections, empowering agents to interact more dynamically with unfamiliar environments. While this enables individuals to disrupt locked-in defection equilibrium, the ephemeral connectivity structurally precludes sustained large-scale cooperation. This persistent limitation has impeded a mechanistic understanding of how ephemeral connectivity, inherently incompatible with sustained interactions, operates within dynamic networks to support cooperation. Here we develop a novel framework that integrates historical interactions with ephemeral connections, capturing the co-evolution of behavioral strategies and dynamic network structures to analyze cooperation mechanisms. The model quantitatively evaluates four key determinants of cooperation: (1) connectivity thresholds to ephemeral ties, (2) memory length for historical interaction,(3) social capacity constraints on individual engagement, and (4) opportunity costs to create connections. Simulation results reveal that cooperation thrives under two key conditions: elevated connection costs and expanded social capacity. Conversely, overreliance on historical interactions proves detrimental to cooperative outcomes. Interestingly, while newly formed ties demonstrate low cooperation levels, they play a critical role in facilitating cooperative cluster formation among established partners, ultimately contributing to enhanced system-wide cooperation. This work establishes an ephemeral connections framework to investigate the co-evolutionary dynamics of cooperation mechanisms, providing novel insights into how cooperation evolves in temporal networks.