Like you, there were things I could hold in my head when I was younger that I cannot now. However, thinking back, it probably had more to do with the fact that

Like you, there were things I could hold in my head when I was younger that I cannot now. However, thinking back, it probably had more to do with the fact that when I was younger my other knowledge was less useful to anyone so it was unlikely I'd get interrupted. Now, I get interrupted much more frequently. Might it be that the people making progress are less interrupted? Also, this sounds like it might be a place where pair programming would be more efficient than two people working alone.