Animation/special effects expert Bill Desowitz has posted an interview with Andy Serkis on Indiewire. In it Serkis talks about new performance-capture techniques that have been developed by Weta since he played Gollum in The Lord of the Rings. One paragraph describes his scene with Bilbo in The Hobbit:

Indeed, that’s what happened when Serkis revisited Gollum after a 12-year absence for “The Hobbit: An Unexpected Journey” (December 14). Shooting live on set provided a more dynamic sense of play in his scene with the young Bilbo Baggins (Martin Freeman). “The way we approached the scene was very much to treat it like a chamber-theater piece, where we could experiment and try different things out,” Serkis explained. “Of course, the other significant change now is that we’re using facial capture, so my facial muscles are driving the facial muscles of the digital puppet.”