(Re)building Cooperation: Effects of a Cognitive Intervention on Cooperative Behaviour in Games.

Cooperation often breaks down when one party appears to withdraw trust, yet most research has focused on initial trust formation rather than how the aggrieved party can resist the impulse to retaliate. In a randomised controlled online trial (N = 318), we tested whether a brief cognitive intervention inspired by Dialectical Behaviour Therapy principles could promote resilient cooperation in the face of trust withdrawals. Participants played a Repeated Trust Game as trustees against adaptive computerised investors driven by hidden Markov models (HMMs) trained on human data, providing behavioural realism under full experimental control. Following the intervention, participants returned a significantly higher proportion of the amount received than an active control group across the post-manipulation game. The groups diverged most sharply at the pre-programmed low investment, where the control group retaliated by reducing returns while the intervention group maintained the same level of returns. This shift occurred without a change in self-reported emotional reactivity, dissociating the preserved emotional reaction from the retaliatory behaviour it drives. HMM analysis of participants' own return patterns revealed that participants in the intervention condition were less likely to become stuck in low-return behavioural states following the pre-programmed low investment, though a notable minority did not respond to the intervention. The intervention effect did not transfer to a Prisoner's Dilemma game, consistent with context-specific effects. These findings provide proof-of-concept evidence that targeted cognitive strategies can support cooperation after trust violations, and show that HMM-based agents are a useful tool for studying social behaviour under controlled conditions.