Large language models exhibit stigmatizing behaviour in contextual judgements of health conditions
摘要
Current fairness evaluations of large language models (LLMs) deployed in healthcare settings largely focus on explicit statements about health-related stigma. Here we show that this may overestimate safety by contrasting explicit stigma-scale scores with contextual judgements in 51 scenarios. Across six LLMs and three high-stigma domains (human immunodeficiency virus (HIV), hepatitis B virus (HBV) and mental health), LLMs scored below the meta-analytic human benchmark on six stigma scales (Nhuman = 56,612). However, in a contextual judgement task with 61,200 model decisions, LLMs showed systematic differences in stigma-congruent judgements across health conditions, with the largest differences observed when mental-health disorders and highly stigmatized physical conditions (HIV/HBV) were compared with healthy baselines. Reasoning-enabled models were associated with smaller health-condition differences. From their reasoning content, we identified transferable prompting strategies that were associated with lower rates of stigma-congruent output in non-reasoning models across languages and scenarios. These findings expose a dissociation in LLM outputs between explicit statements and contextual judgements in the evaluated versions, and argue for context-sensitive audits of LLMs before health deployment.