TV Guide: For an eight-year-old, we certainly know a lot about Lisa Simpson’s interior life.

YEARDLEY SMITH: I think that it was a well that needed to be tapped, sort of a balance between Homer’s silliness and Bart’s antics. She’s sort of the humanity of the show. Really humanity is too strong a word, but she brings that sort of cathartic element to the show. But you couldn’t have that all the time. Because it’s not a drama, it’s a half hour comedy.

TVG: What does Lisa yearn for?

YS: She craves understanding and a sense of belonging. She’s quite the loner, and really struggles to figure out where she fits in. And I think that’s a source of enormous sadness for her, as it would be for any 8-year-old. To feel as though you don’t really belong.

TVG: It’s stated so well in the show’s opening every week, when Lisa goes off on that saxophone riff…

YS...and gets chastised by the teacher and sent out of the room. That, in itself, is a great commentary of the whole arc of the character. Lisa is so contained and self-sufficient that when she actually expresses a need and doesn’t get it, I think it’s incredibly heart breaking. So you really pull for her. She’s not reckless or shallow about her needs; she chooses them carefully. And so you rarely hear from her in that regard, so when you do, you really, really, really want her to get it.

TVG: There have been moments when she’s actually been like a mother to Marge in expressing those very things. In a way, Marge learns from Lisa.

YS: Yes, which again, given Lisa’s particular struggle, I think is a very heartfelt moment for her to be able to say "I don’t often succeed in this area, but I know that you should never stop fighting for what you want. So I encourage you as I encourage myself to do that." She’s a great little character, I’m enormously fond of her.