Life Tonight's film class dealt with the of importance in an actor's perforance within a film. Some more clips from Bresson pieces were shown, Pickpocket and Mouchette. My understanding was that its better if the performer understates or even loses altogether the pretence of trying to copy what happens in real life, or rather trying to present a certain preset expected set of emotions, in other words be artificial. Instead they should just be presenting the lines and actions within a space and letting everything else in the film, the photography, editing and music tell the story and evoke whatever emotion is needed.
I can absolutely understand that point of view and I've seen it in action all over the place, either on purpose (Jean Reno in Leon) or inadvertantly (Keanu Reeves in everything). But it obviously wouldn't work in every situation. Although Buster Keaton was mentioned it doesn't seem like something that could work in overtly comic films unless the lack of emotion was the point. When Harry Met Sally would have lacked a certain ... urgency ... in places.