Canadian director David Cronenberg's new film about the birth pangs of psychoanalysis, A Dangerous Method, screened at the Venice Film Festival on Thursday. Since then, it's been praised in early reviews as "elegant and restrained" and "precise, lucid and thrillingly disciplined" – but the real buzz is about Keira Knightley's performance as a young woman suffering from psychotic hysteria.

The film follows the relationship between Sigmund Freud and his protégé, Carl Jung (played, respectively, by Viggo Mortensen and Michael Fassbender). Knightley plays Sabina Spielrein, who came under Jung's care as a teenager and had a love affair with him before launching her own career as a psychoanalyst.

The Hollywood Reporter's Todd McCarthy praises "Knightley's excellent work" in an extreme performance: "Screaming and alarmingly jutting out her jaw in extremis, Knightley starts at a pitch so high as to provoke fear of where she'll go from there. Fortunately, the direction is down."

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Likewise, Xan Brooks in The Guardian writes that Knightley provides "the Oscar bait" for the film.

But Justin Chung, in a generally positive review for Variety, described Knightley's performance as a potential problem area: "The spectacle of the usually refined actress flailing about, taking on a grotesque underbite, and stammering and wailing in a Russian accent is perhaps intended to clash with her co-stars' impeccable restraint, but does so here in unintended ways."

He goes on to write that "Mortensen's Freud, a sardonic, ineffably sinister presence who rarely raises his voice above a silky-smooth purr, calmly steals the picture."

David Gritten, meanwhile, comes down in the middle in his review for The Telegraph, describing Knightley's performance as "so ferocious in those early scenes that it seems likely to become the film's main talking point."

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The film is based on Christopher Hampton's 2002 stage play The Talking Cure, which in turn was based on John Kerr's 1993 non-fiction study, The Most Dangerous Method: The Story of Jung, Freud and Sabina Spielrein, which described new revelations from boxes of Spielrein's papers and letters, discovered in the 1970s and 1980s.

Cronenberg's film will also be screening at this year's Toronto International Film Festival, opening next week.