The stigma of mental illness: Testing for the implicit bias in diagnostic labels

•The Who-Said-What-task can measure implicit mental illness based categorization.•Implicit categorization is found for the labels schizophrenia and depression.•Small associations with explicit stigmatization were found. Several models that attempt to explain stigmatization of people with mental illness emphasize the relevance of social categorization. However, research on illness-based social categories has been limited to explicit self-report measures. In this study, we explored whether implicit social categorization based on mental illness labels can be assessed with the “Who-Said-What” (WSW)-paradigm. In this paradigm, participants have to allocate a large number of statements to individuals who belong to different social groups (e.g., mentally ill vs. healthy). Due to the amount of statements, errors in allocation are to be expected. A disproportionate amount of erroneous allocation to individuals within a social group is interpreted to indicate implicit social categorization. In three studies, we (1) pilot-tested a WSW-paradigm for mental illness categorization (n = 24), (2) replicated these findings in an independent, larger sample (n = 85), and (3) aimed to rule out alternative explanations for the implicit categorization effects with a modified WSW-task and novel stimulus material (n = 137). We found consistent implicit categorization effects with overall medium to large effect sizes (range: 0.41 ≤ d ≤ 1.01). Implicit components of mental illness based social categorization can be assessed with the WSW-paradigm. Future research needs to explore the interrelations of implicit categorization, implicit vs. explicit stigmatization and discriminating behavior.