In recent years, more and more mental health research relies on large-scale online testing. Researchers get hundreds of participants to fill out many mental health questionnaire, and then identify links between their psychiatric tendencies (as revealed by their questionnaire responses) and their behaviour in controlled tasks. Using this method, previous research identified robust links between mental health (compulsivity, depression and anxiety) and decision confidence. In this collaboration with Noam and Ruvi, we show that these correlations are largely driven by factors outside mental health, namely participants’ response biases and their level of attention.