Writing for the Milwaukee Journal Sentinel, Duane Dudek speculated that Johansson's character assumes a human identity to collect information about humans as an alien intelligence might, inducing an identity crisis causing her to "spin out of control like a broken machine". He wrote that the motorcyclist can be interpreted as a companion, enabler, or pursuer, and that the "tar-dark world" where the woman submerges her victims may be a nest, a web, another planet or dimension, or a visual representation of how sex feels to her or them.[6] In the Guardian, Leo Robson wrote that Under the Skin deals with race and immigration. He interpreted Johansson's character as a "kind of immigrant", and that the film's title "seems like part of an anti-racial slogan, a reminder that despite our racial or ethnic differences we share some basic components".[7]
Critics highlighted the exploration of empathy as a defining human capacity, with Johansson's character coming to share in this over the course of the film.[8][9][10] Noting that a turning point occurs during Johansson's character's encounter with the man with facial tumours (played by Adam Pearson), the philosopher Colin Heber-Percy wrote: "The film suggests it is our very weakness which we value, which makes us us. [...] [The alien] recognises herself in the world, in the middle of things; she recognises herself as subject among subjects. In short, she chooses (or cannot fail to choose) to become human, to empathise, to be weak as flesh."[11] The lecturer Maureen Foster, who highlights Johansson's character's examination of herself in the mirror before releasing Pearson's character, writes that the film presents empathy as "a definition for what is human", with the alien discovering "something in herself that was either lost or had never been there in the first place."[12]
Though Glazer said he wanted to make a film "more about a human experience than a gender experience",[13] several critics identified feminist and gender themes. The Economist wrote that "there is some aggressive sexuality in the film: women seem very vulnerable but then men's desires are punished".[13] In The Mary Sue, Kristy Puchko wrote that Under the Skin "creates a reverse of contemporary rape culture where violence against women is so common that women are casually warned to be ever alert for those who might harm them ... By and large men don't worry about their safety in the same way when walking home late at night. But in the world of Under the Skin, they absolutely should."[14]
Robson wrote that Johansson's character is "both a watcher and predator of men. In the society she enters, and to which she brings nothing besides a body, [she] is a sex object, in dress and demeanour a kind of sex toy; she might have come to Earth to prove a point about male expectations of women ... If Under the Skin communicates any gender-politics message, it does so through the disparity in excitement between the male characters' reaction to [Johansson] and that of the camera."[7] The Atlantic journalist Noah Gittell noted how little hype Johansson's nude scenes attracted, despite her status as a Hollywood sex symbol, and wrote: "The way the film frames it — with Johansson having removed almost all of her personality from the character — it doesn't play as even remotely sexual, and the scene, remarkably, barely attracted any hype."[15]
The film is thought to be inspired by the Scottish folklore of Baobhan sith, female vampire-like creatures who prowl during the night preying on men.[16]
