When they are speaking about a passion, respond to children as if you would a tenured professor at a prestigious university, and to an adult as if you would a child free of the burdens of adulthood.
Children are desperate to teach the wonders of the world that they know, that they have just learned, and share it with anyone interested. Adults pour passion they didn’t know they had into voluntary obligations, and crave a simple acknowledgment of that passion as being worthy and valid.
“Dear third grader, tell me exactly why you chose <x> as you third favorite carnivorous dinosaur instead of second, as specifically as possible.”
“Hey neighbor, your vegetable garden is absolutely gorgeous this year…and no I’m not just saying that because the tomatoes you gave me last year were absolute perfection.”