What a great word.
1. The quality of being easily shaped or moulded.
2. The adaptability of an organism to changes in its environment or differences between its various habitats.
Plasticity very much describes our ever-adapting ear/brain mechanism.
Unlike our test equipment which we rely upon to be solid and unchanging, our ear/brain mechanism is constantly changing, adapting, and learning. It is why we can identify with remarkable accuracy the most delicate of sounds: one violin from another, the tiniest of changes in vocal presentations. And we can do this all throughout our lives despite the fact our ears aren’t working as well as they once did.
If I owned a piece of measurement equipment that was constantly changing and adapting I’d send it in for repair. Microphones, analyzers, scopes, and test gear are only valuable to the extent they are unchanging. They are a reference.
Fortunately, our ear/brain mechanisms are the exact opposite.