Abstract
Can exposure to a forgiving, consistently trusting partner improve interpersonal cooperation? Attachment theory suggests positive relational experiences can correct negative internal working models, but individuals high in rejection sensitivity (RS), characterized by anxious expectations of rejection, may be resistant to such corrective experiences due to stable negative expectations. We tested this using a randomized experiment (N = 206) in which participants played repeated trust games with HMM-based artificial agents that simulate human-like trust dynamics. After a baseline game, participants were exposed to either an idealized partner (an agent designed never to remain in a low-trust state, free from pre-programmed trust withdrawals, and consequently investing more; Manipulation) or a standard agent maintaining typical trust withdrawal patterns (Control), then played a final game with the standard agent; these features were varied together, so the design tests their joint effect. In the primary, powered contrast, exposure to the idealized partner reduced subsequent cooperation, and participants rated the unchanged post-exposure agent less favorably, a pattern consistent with a negative contrast effect, an interpretation developed after initial analysis. RS moderation was a planned analysis but was not separately powered: we detected no moderation of the reduction by RS, and an apparent RS difference in responsiveness to partner investment was not robust once participant-level variation in responsiveness was modeled. These findings suggest that brief exposure to an idealized partner does not universally promote cooperation and can reduce it, and point to expectation-updating, rather than exposure alone, as one candidate target for future interventions.