arXiv subjects

Yuta Kido

Publications and source records attributed to Yuta Kido.

2 recordsLinked to original sources

arXiv2026

Reputation and institutional certification as complementary trust mechanisms in a single online market

Reputation and institutional certification are the two main trust mechanisms under information asymmetry, yet their interaction remains poorly understood. We analyze nearly one million fixed-price eBay listings of Pokemon cards, where sellers choose among three signals: third-party grading (institutional certification), self-grading (a self-claimed condition description), or no signal. We show that self-grading and third-party grading dominate distinct regions of the reputation-value space, with the self-grading region widening as reputation rises. Reputation also amplifies the price premium of self-grading but not that of third-party grading. We develop a signaling game in which a false self-claim carries an ex-post cost proportional to reputation, whereas certification carries an ex-ante cost independent of reputation. These costs split the reputation-value space into equilibrium regimes that explain both patterns. The two mechanisms are therefore substitutes within a transaction yet complements across the market, replacing the reputation-versus-institution dichotomy with a regime structure set by reputation and value.

physics.soc-ph↗

arXiv2026

Partial exploiters sustain cooperation: the hump-shaped strategy stably coexists with unconditional cooperators

From collective hunting to environmental problems, social dilemmas are pervasive in human societies. Prior research has documented highly heterogeneous behavioral patterns in such settings. However, how this heterogeneity emerges and how it shapes large-scale cooperation remain unclear. Here, we focus on a robustly observed but underexplored pattern: the hump-shaped strategy (Hump). Individuals adopting Hump match others' contributions up to a threshold, only to reduce their own above it. Using agent-based simulations across group sizes and production-function shapes, we find that Hump is individually adaptive, especially in intermediate-sized groups with step-like production functions. Despite its exploitative nature, Hump also elevates population-level cooperation. The underlying mechanism is that Hump can form a stable equilibrium with unconditional cooperators (AllC), which jointly exclude defectors across a broad range of environments. Our findings suggest that underexplored patterns of behavioral heterogeneity -- including both Hump and AllC -- play a functional role in sustaining large-scale cooperation.

physics.soc-ph↗