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  • Open Access

Offer of a reward does not always promote trust in spatial games

Haidong Zhang1, Chaoqian Wang2,*, Shuo Liu1, Charo I. del Genio3,4,5, Stefano Boccaletti3,6,7, and Xin Lu1,†

  • *Contact author: CqWang814921147@outlook.com
  • †Contact author: xin.lu.lab@outlook.com
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Phys. Rev. Research 8, 013283 – Published 13 March, 2026

DOI: https://doi.org/10.1103/8992-hzsq

Abstract

Trust is one of the cornerstones of human society. One of the evolutionary pressure mechanisms that may have led to its emergence is the presence of incentives for trustworthy behavior. However, this type of reward has received relatively little attention in the context of spatial trust games, which are often used to build models in evolutionary game theory. To fill this gap, we introduce an inter-role reward mechanism in the spatial trust game, so that an investing trustor can choose to pay an extra cost to reward a trustworthy trustee. With extensive numerical simulations, we find that this type of reward does not always promote trust. Rather, while moderate rewards break the dominance of mistrust, thereby favoring investment, excessive rewards eventually stimulate a nonreturn strategy, ultimately suppressing the evolution of trust. Additionally, lower reward costs do not necessarily promote trust. Instead, more costly, but not excessive, rewards enhance the advantage of the original investment, consolidating the clusters of rewarders and improving trust. Our model thus provides evidence about the counterintuitive nature of the relationship between trust and rewards in a complex society.

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Information

Phys. Rev. Research 8, 013283– Published 13 March, 2026
  • Received 21 November 2025
  • Accepted 20 February 2026
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Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.

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