This is McArthur Wheeler. In 1995, he robbed two banks in Pittsburgh in broad daylight, with no disguise. He smiled at security cameras, fully believing he was invisible. Why? He had covered his face with lemon juice.
Wheeler thought lemon juice worked like invisible ink - if it could make writing disappear, surely it could do the same for his face. He even tested his theory by rubbing lemon juice on his skin and taking a selfie. When his face didn’t appear in the photo (likely due to bad lighting or a camera issue), he took it as confirmation that his "invisibility cloak" worked.
This story caught the attention of professor David Dunning and inspired him, alongside his graduate student Justin Kruger, to conduct a study to explore how people assess their own competence. In their 1999 paper, "Unskilled and Unaware of It," they found that when people lack knowledge or skill in a particular area, they often lack the ability to recognise their own limitations. In other words, the less we know, the more confident we may feel - because we don’t yet understand what we’re missing. This phenomenon became known as the Dunning-Kruger Effect.
The lesson? We don’t know what we don’t know.
When designing learning, we have to remember that people might not realise they need to learn. The best way to reveal hidden gaps is to start with practice, not theory. Let mistakes do the teaching, use reflection to surface blind spots, and create moments where people see what they don’t know. And remember your barrier to accessing learning - if it doesn't feel relevant, it won't be used.
Great story right? I recently found myself in a bit of a rabbit hole exploring the wild origin stories behind well-known behavioural science theories and concepts, and found it super fascinating so will be sharing more - let me know what you think of this one! :)