Here's my wild guess: the DK effect is nothing more than people's unfamiliarity with situations involving percentiles. In school, <60% is failing. So intuitiv

Here's my wild guess: the DK effect is nothing more than people's unfamiliarity with situations involving percentiles. In school, <60% is failing. So intuitively 50% seems like a modest guess if you really suck at something. If people were more familiar with situations where they were stack-ranked with their peers and saw numbers like 15%, their intuition would be better calibrated. The curve between estimated performance and actual performance has the right shape, it's just the calibration that's off. But it became a popular phenomenon because it allowed people to project flattering beliefs about themselves onto scientific data.