https://astralcodexten.substack.com/p/skills-plateau-because-of-decay-and

Followup to: Why Do Test Scores Plateau; Ritalin Works But School Isn't Worth Paying Attention To

Why Do Skills Plateau?

Economist Philip Frances finds that creative artists, on average, do their best work in their late 30s. Isn't this strange? However good a writer is at age 35, they should be even better at 55 with twenty more years of practice. Sure, middle age might bring some mild proto-cognitive-impairment, but surely nothing so dire that it cancels out twenty extra years!

A natural objection is that maybe they've maxed out their writing ability; further practice won't help. But this can't be true; most 35 year old writers aren't Shakespeare or Dickens, so higher tiers of ability must be possible. But you can't get there just by practicing more. If acheivement is a function of talent and practice, at some point returns on practice decrease near zero.

The same is true for doctors. Young doctors (under 40) have slightly better cure rates than older doctors (eg 40-49). The linked study doesn't go any younger (eg under 35, under 30…). However, Goodwin et al find that only first-year doctors suffer from inexperience; by a doctor's second year, she's doing about as well as she ever will. Why? Wouldn't you expect someone who's practiced medicine for twenty years to be better than someone who's only done it for two?