The Clairvoyant Zoopraxiscope

Saw Monster yesterday and was struck at various points by the question: am I watching a less than stellar performance inside a shell of nervous-making makeup? Wuornos, when in a social milieu, always looks much more affected than those around her, although we know that they're all extras, working for less than Theron, of course, but nevertheless mindful of mimesis. I would have to do a little digging to find out if the postures that Theron assigned to Wuornos, including one (her most common) in which she looks like someone is pulling her shoulders back behind her, were genuine...