I think there's some of the well-known "Thinking, Fast and Slow" (https://en.wikipedia.org/wiki/Thinking,_Fast_and_Slow) thing going on as well. As we age, we gain knowledge and insights that we try to reconcile with as we learn new things, and that takes longer. E.g., if you're learning the theory of music scales, those with a math background will tend to think of the math behind the notes as they learn, which is the "Think Slow" way (with active analysis) and takes longer but results in a deeper understanding.