Dunning and Kruger noted that while everyone seems equally likely to delude themselves, there is one key difference between those who are confident yet unable (stupid) and those able yet lacking in confidence (intelligent)
— how we deal with and integrate feedback into our behaviour.
In the opening example, a guy covered himself in lemon juice before robbing a bank, thinking the juice would make him invisible.
When he was caught he was “incredulous on how his ignorance had failed him” even when he had absolute confirmation (being in jail) that it did fail him.
During their research, Dunning and Kruger noted that good students would better predict their performance on future exams when given accurate feedback about the score they achieved currently and their ranking. When the bright student was told that s/he had scored a 94% and was ranked 3rd in the class, (for example) s/he would then see him or herself at their true level.
The poorest-performing students would not change their predictions even after clear and repeated feedback that they were performing badly. They simply insisted that their assumptions were correct.
Hence, the student who scored 30% on the exam, and was ranked 46th in a class of 47 did not stop and go back, and check their errors and try to do better. The Stupid student continued to believe they were high scoring.