I ... thought this was common knowledge. I learnt how to wiggle my ears when I got startled by a book falling from a shelf and my ears instinctively "raised".

I ... thought this was common knowledge. I learnt how to wiggle my ears when I got startled by a book falling from a shelf and my ears instinctively "raised". Picture a dog going from "idling" to "alert", with the ears pointing up. It was like that, but for humans. I then said "Ooooh, so that's how you do it". There has never been a doubt in my mind that the muscle is connected to "alert, listen closely".