I've been reading a few books about the human brain and music lately, and both are by people I've interviewed. One is Susan Rogers' [Tape Op #117] and Ogi Ogas' This is What it Sounds Like: A Legendary Producer Turned Neuroscientist on Finding Yourself Through Music. The other book, which I'm still digging into, is Daniel Levitin's [#74] I Heard There Was a Secret Chord: Music as Medicine.
I love reading books that focus on how we assimilate and react to sound, and as the authors point out, recent neural mapping shows a wide range of activity across many parts of the brain when listening to or (especially) playing music. Looking into all this research led me to the concepts of fluid intelligence versus crystallized intelligence. Generally speaking, fluid intelligence can be defined as the ability to assess, learn, and act when confronted with a new problem or situation. Crystallized intelligence, however, applies to decision-making based on accumulated knowledge.
Years ago, when working with engineers that were older and/or more experienced than myself, I would wonder how they made the recording process look so effortless, and why their tracks always sounded way better than my own work, even when we used identical gear in the same room. While we, as humans, obviously gain crystallized intelligence as we age, we also gradually lose our ability to harness fluid intelligence. Some sources say fluid intelligence peaks at 40, with crystallized intelligence peaking at 60 or 70.