Micaela lives here in Japan and explains the Japanese "culture" of aizuchi.
I've actually picked up several of these thanks to my students and friends. I especially say hmm, uhn, and ehh. I haven't really started using any of the Japanese "true" words ("so desu ne", etc) though I certainly understand them at this point!
So if you ever speak to a Japanese person - or someone who's been here for a long time - don't be surprised by this!