Question about the acting/directing style?

I know almost nothing about acting styles, and I realize that, more or less, the actors in a movie act precisely the way that the director tells them to. This movie is pretty good, and I loved Napolean Dynamite, but is there a particular name that can be applied to this particular acting or directing style? There is no question that the actors in both movies are extremely talented and are capable of a convincing performance no matter what kind of movie they are in, but I'm going a little crazy trying to figure out what to call their performances in those two films.