It may seem counter intuitive or perhaps rather disconcerting that there is no firm evidence that psychotherapists become more effective as they become more experienced (Tracey et al., 2024). In fact, there is some evidence that psychotherapists become less effective as they become more experienced (Erekson et al., 2017; Goldberg et al., 2016). This lack of a relationship between therapists’ experience and their effectiveness is especially challenging as it is well established that therapists tend to overestimate their clinical effectiveness through self-assessment bias (Walfish et al., 2012). Another relevant but problematic finding is that older, more experienced therapists tend to judge themselves as more effective than younger, less experienced practitioners (Orlinsky & Rønnestad, 2005; Parker & Waller, 2015).