When Are Psychiatric Patients Considered Less Credible? Implications for the Epistemic Injustice Debate

Philosophers have argued that people with psychiatric conditions are vulnerable to epistemic injustice because their testimony is systematically, and unjustly, discredited relative to psychotypical individuals. Whether such differences in credibility amount to epistemic injustice is a normative question, yet whether and how they occur is an empirical one. In five pre-registered experiments (N = 1,908) on Prolific, we tested whether and when people grant less credibility to psychiatric patients’ testimony compared to other patients and to individuals without any medical condition. We used vignette-based designs depicting both clinical and non-clinical settings to compare credibility attributions across these groups of speakers, and an incentivized prediction game to elicit beliefs about others’ attributions of credibility in these contexts. Overall, our experiments reveal that psychiatric patients’ testimony is deemed slightly less credible than the testimony of comparable non-patients in tightly matched comparisons. This surprisingly small effect was due partly to individual differences in its magnitude: participants who moralized epistemic injustice were least likely to discount psychiatric patients’ testimony, while participants who were skeptical of the phenomenon showed a stronger tendency to treat psychiatric patients as less credible than psychotypical speakers. These findings support the claim that psychiatric patients are granted reduced credibility by some audiences–in particular, by those who are least likely to view epistemic injustice as a genuine problem–a key empirical premise in the debate on whether psychiatric patients are vulnerable to epistemic injustice.