When Procedural Fairness Fails: The Role of Conspiracy Mentality in Shaping Institutional Trust

Procedural fairness refers to institutional decision-making that is transparent, neutral, predictable, and attentive to citizens’ voices. Prior research provides robust evidence that procedural fairness fosters institutional trust across diverse contexts. However, less is known about whether this effect is uniform across individuals or moderated by psychological differences. One potential moderator is conspiracy mentality – a general tendency to interpret significant events as secret plots by malevolent groups. This mindset has been shown to remain relatively stable and immune to external influences. Therefore, this study examines whether conspiracy mentality moderates the impact of procedural fairness on trust in institutions. We focus on four sources of procedural fairness: giving voice to citizens, giving voice to experts, transparency about decision-making reasons, and predictability of institutional actions. Trust is conceptualized along two dimensions: acceptance of vulnerability and suspicion toward institutional actions. A vignette experiment was conducted as a part of a broader survey of older Czech adults (N = 667; aged 50+, M = 64.6; 57% women). Participants read one of 12 narratives describing a fictitious government deciding on pandemic measures, varying in voice (citizens, experts, absent), transparency (present vs. absent), and predictability (present vs. absent) in a 3x2x2 between-subject design. Trust perceptions were then assessed. Factorial ANCOVA controlling for age, gender, interpersonal trust, and trust in the current government revealed that trust (greater acceptance of vulnerability, lower suspicion) was most strongly increased by transparency, followed by citizen and expert voice. Predictability showed no effect. Conspiracy mentality predicted lower trust overall and moderated the effect of transparency: transparency increased trust only among individuals with low or moderate conspiracy mentality, not among those high in it. These findings suggest that the benefits of institutional transparency for trust are contingent on conspiracy mentality. Individuals high in conspiracy mentality appear cognitively resistant to transparent institutional behavior, indicating that alternative trust-building strategies may be necessary for this group.