Hmm, that doesn't sound like the same melody to me...
I agree that they are likely two different pieces, with the TAL piece being merely stylistically similar (perhaps deliberately).
So specifically, the *exact* piece being played in the This American Life piece is what you're after? Or are you just trying to figure out the original piece, the one that you think it was reminding you of, the one you've heard before that you can't quite place?
Those might be two different things, they were for me: When I heard the bit in This American Life, I also thought it sounded like something I'd heard before, and after a bit of googling, as soon as I heard Carnival Of Souls, I realized that *that* was the one I'd been thinking I'd heard before.
As far as the exact piece goes: Something in the back of my brain is saying Decemberists, but I don't know exactly why. I have no information or examples to back that one up.