That’s true, particularly for medicine, but I wonder how far it applies to trading? In the natural sciences the art is in controlling the conditions to get reproducible outcomes and interpreting the results. In trading though this is very difficult because markets are basically chaotic and it’s very hard to create reproducible conditions. There are undoubtedly a few skilled traders who succeed on merit, but for the vast majority success is down to dumb luck (which their ego interprets as raw talent of course) over the short term. Over time they will revert to the mean - or perhaps not even that. There is a fascinating study of stockpickers by the economist Daniel Kahneman The Illusion of Stock-Picking Skill which is really worth a read.
Briefly, the tldr; is that he studied the performance of 25 investment advisors over 8 years and found almost zero correlation between their performance year on year. The ‘successful’ advisors were those who in their early years had had a lucky roll of the dice. In fact some of the ‘successful’ advisors he studied did significantly worse than chance.
Many individual investors lose consistently by trading, an achievement that a dart-throwing chimp could not match.
He also says:
The evidence from more than 50 years of research is conclusive: for a large majority of fund managers, the selection of stocks is more like rolling dice than like playing poker. At least two out of every three mutual funds underperform the overall market in any given year.
They are only ‘successful’ because it’s a closed system propped up by bonus schemes and individual and company reputations.
While this is a slightly different field from currency trading, I’d be willing to bet the same rules apply. Certainly worth thinking about before you put on your water wings and go swimming in the shark pool (or wandering in the Trollbox).