When people acquire a bit of knowledge about a discipline, their overconfidence leads to arrogant ignorance, a state where beginners think they know more than they actually do. As the complexity and confluence becomes apparent, their confidence often drops at or below the initial state of understanding before gradually rising again as genuine expertise develops.
Kruger, J., & Dunning, D. (1999). Unskilled and unaware of it: How difficulties in recognizing one's own incompetence lead to inflated self-assessments. Journal of Personality and Social Psychology, 77(6), 1121-1134.
https://doi.org/10.1037/0022-3514.77.6.1121 People who perform poorly on tests of humor, logical reasoning, and grammar systematically overestimate their performance and abilities. This overestimation occurs because the same lack of skill that leads to poor performance also prevents them from recognizing their incompetence - both in themselves and in others. The pattern shows that those in the lowest quartile of actual ability consistently rate themselves as above average, while those with higher ability tend to slightly underestimate their performance relative to others.
The original Dunning-Kruger study found that people with low ability in a domain (logic, grammar, humor) significantly overestimated their performance, while those with high ability slightly underestimated theirs. But their research didn't track the same individuals over time as they gained expertise. However, the actual Dunning-Kruger research did not track individuals over time as they gained expertise, nor did it measure a confidence curve that rises, falls, and rises again. Their study simply compared four quartiles of students' performance on tests and found that those in the bottom quartile overestimated their abilities relative to peers.
The "Mount Stupid" and "Valley of Despair" terminology appears to be a popular interpretation or extension that has been widely circulated online, but these terms do not appear in the original Dunning-Kruger research. The beautiful curve showing confidence starting at zero, spiking, nose-diving, and climbing again has no evidence from their actual study.