Age factor is absolutely real in well studied skills such as chess.
There are no instances of people starting to play chess after say age 25 and becoming a grandmaster say after 20 years at 45. Plenty of people who start at 10 or earlier and become grandmasters before 25.
Lack of deliberate practice is surely not the only explanation.
Starting at age 15 is already considered very late for chess. (Anecdata: I started at 10 and peaked at FM coming close to IM norm once)
Internet is awash with late bloomer examples in various fields (such as writing). However when you look closer you see that the persons in question had serious related practice at an earlier age..
I am yet to find an example of someone taking up a completely new skill after 40 and achieving notable greatness. Like champion of your city at tennis or master in chess, etc.
So my formula is skill = STARTING_AGE X coef1 + GENETICS X coef2+ DP X coef3
Only questions is what values to give coef1, coef2 and coef3
Oh I totally agree. My only point would be, I think older people tend to over-estimate coef1 and under-estimate coef3. In other words, since aging has an effect on speed of skill acquisition, people over 30 might be more likely to blame that for the fact that their struggling and give up on something they could pick up quite decently with a bit more practice.
Also, when you talk about "related practice at an earlier age", I also think this is nothing to scoff at. As I have gotten older I've often found that a very real route to solving novel problems is to figure out how to apply something tangentially related that I already know.
There's also a correlation does not imply causation in this. People get worse at acquiring new skills compared to a younger person but there's lots of things that change with age outside of physical fitness. For instance, a kid delegates all worries outside of studying and games to the parents. Experts at fields might also underperform in some school subjects in favor of focusing in those they enjoy the most, so they can optimize their time even further.
And then we come to the society component. Anyone seeing a 12 year old shipping an app in the app store will omit the fact that the kid might be receiving training from an expert (maybe even a family member) since the age of 4. They won't judge it as "a person who learned programming for 4 years and shipped an app" but "a 12 year old that shipped an app". You might think the difference is semantic but if I were to told you that I was learning programming for 4 years and shipped an app you'd be like "what do you want now, a cookie? You're 30".
People who believe that over a certain age you're not gonna do anything good might consider suggesting software development as an activity to a 40 year old as a hobby, not as a profession. I cannot imagine them telling the same thing to a child. Don't get me wrong. I do believe that physical change exists and that my 15-year old self would run circles around me. But everyone gives advice on the grounds of seeking masters, not professionals. Translate that belief to the hiring process and it's easy to see where ageism starts. Someone might say that hiring a 40 year old who wants a junior developer position is "settling for less" in spite of the fact that your product can be shipped just as efficiently.
There are no instances of people starting to play chess after say age 25 and becoming a grandmaster say after 20 years at 45. Plenty of people who start at 10 or earlier and become grandmasters before 25.
Lack of deliberate practice is surely not the only explanation.
Starting at age 15 is already considered very late for chess. (Anecdata: I started at 10 and peaked at FM coming close to IM norm once)
Internet is awash with late bloomer examples in various fields (such as writing). However when you look closer you see that the persons in question had serious related practice at an earlier age..
I am yet to find an example of someone taking up a completely new skill after 40 and achieving notable greatness. Like champion of your city at tennis or master in chess, etc.
So my formula is skill = STARTING_AGE X coef1 + GENETICS X coef2+ DP X coef3
Only questions is what values to give coef1, coef2 and coef3