Mental processes of chess masters revealed how people become experts (2016) [pdf]

Gives some context for the kinds of fields where deliberate practice improves performance.

First, you are dramatically, 110% right that pop psychology books plunder really valuable research such as this for ultimately banal insights that they manage to hide in a 300 page book that could be 10 pages.

K. Anders Ericsson, the absolute giant in the field of expertise research, is quite dismissive of Malcolm Gladwell and upset at his mis-interpretations of his work. Go look at his book, "Peak", which goes into depth on this (and funny enough looks like every other stupid pop psychology book, although it is not).

Finally, if you want to explore the best research we have from the present through the last 40 years, highly recommend you check out "The Cambridge Handbook of Expertise". It's 40 chapters written by nothing but PhDs.

They compare what expertise means across History, Firefighting, Surgery, Ballet, even Truck Driving and Software Design.

If I look at deliberate practice in musical proficiency amongst the general populace, it'll look like deliberate practice is responsible for almost all of the proficiency. However, if I look at the top 100 musicians in the world, they would have all practiced thousands of hours and I expect practice to have diminishing returns, so it should be responsible for very little of the variation in their ability.

I would expect also that in more multifactorial activities which are often the basis of professions that it is both A) difficult to ascertain what expertise is (often reducing to an empty social credential) B) difficult to evaluate what good deliberate practice is.

The meta-analysis talks about such factors as the predictability of the environment correlating with the effect size of deliberate practice. I think that's just the tip of the iceberg.