Your general learning capabilities decline with ageing.
Also it's not about learning nowadays. It's about switching. Switching between similar technologies. Using NoSQL/Node.js/FancyMvc.js is not learning - it's same ol' deep inside. Reading about quantum computing is learning.
30. Supposedly way past my peak. Haven't felt it. Actually, it seems to be the reverse. When I was 10 years younger, I'd think I understood a topic with only a superficial knowledge. Now, I'm older and I'm better at learning, but I also know what I don't know.
My clock speed is probably 5 to 10% slower than at peak (mid-teens) and will probably slow by another ~2-5% each decade, but software quality keeps going up and, as you probably know, clock speed isn't the most important factor when it only varies by a few percent.
Common, thirty is not old at all :). I meant 40+ - exponential decline rather than linear one. Naturally 30-35 is like a sweet spot between experience and speed.
PS: being 28 myself I am more of a concerned theoretician; I know three people who are 35-40 and quite better than me.
There really isn't a strong case either way on the matter of mid-life cognitive decline. The peak is "somewhere" between 17 and 70, but the plateau is so flat that it's hard to pinpoint it to a specific age and it seems to depend a lot on the individual.
We still don't know when we peak. I tend to take that as a positive.
Where there is exponential worsening is in physical health: risk of death (also, risk of cancer) go up at about 9% per year, or a doubling each 8 years-- that's the Gompertz model, and it holds well from about 20 to 85. For mental decline, though, evidence for general decline in healthy people is pretty thin.
