The Dunning-Kruger effect, first introduced by Kruger and Dunning in 1999, describes a robust and counterintuitive phenomenon: people who perform poorly at a task are often unaware of their lack of competence, and may even overestimate their ability. In their original studies, participants completed tests on humour, logic, and grammar, then estimated their own performance and ability. Those in the bottom quartile consistently overestimated both, believing they had performed above average. In contrast, top performers tended to underestimate their relative skill. This miscalibration stems from a simple yet profound insight: the same knowledge needed to perform well is often the knowledge required to recognise what ‘good’ looks like. When we lack competence, we may also lack the insight to know it.
In the years since, the effect has been replicated across a wide range of domains, including academic performance, emotional intelligence, driving ability, and leadership. The 2011 chapter by Dunning provides a detailed reflection on over a decade of findings, tracing the psychological roots of this pattern and addressing common misunderstandings. Crucially, the effect is not about general overconfidence or arrogance. Rather, it is a cognitive phenomenon linked to gaps in metacognitive skill, or the ability to assess one’s own thinking. Importantly, the pattern also shows that improving someone’s skills can help them better calibrate their self-assessment. As knowledge increases, so does awareness of the standards that define competence.
Dunning highlights that while the most extreme forms of miscalibration occur at the lower end of performance, we are all vulnerable to some form of it. The cognitive bias is not limited to any one group or domain. It reflects a broader human tendency to form intuitions that feel accurate, even when they are not. This has implications for any setting that relies on self-judgement, including workplace learning, leadership, and decision-making.
For leaders focused on inclusion, the implications are significant. Many aspects of inclusive practice, such as recognising bias or managing diverse teams, rely on self-awareness and interpersonal skill. However, individuals may overestimate their competence in these areas, particularly when they have limited exposure to diverse perspectives or have not received specific feedback. This makes it easy for leaders to assume they are inclusive, even in the absence of evidence. One-off training may increase confidence more than competence, especially if leaders are not given opportunities to apply learning or receive developmental feedback. To counteract this, organisations must create structured opportunities for feedback, reflection, and practice. Assessment tools, coaching, and dialogue can help surface hidden gaps and build the metacognitive skill required for inclusive leadership. Competence in inclusion is not just about knowing what to do, but also about recognising when we may not yet know enough.
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