Humans fail to fully understand the world around them and to recognize their limited understanding. The illusion of explanatory depth (IOED) exemplifies these failures: people believe they understand the world more than they actually do and only realize the illusory nature of this belief when they attempt to explain phenomena. An unexplored factor of the IOED is how people may become overconfident by confusing their own understanding with others’ understanding. In three experiments, I compared the IOED in devices, where it is typically examined, with mental health, a domain where society has a more limited understanding. In Experiment 1, I demonstrate that laypeople believe society understands mental health less than devices and that people...