There’s an old showbiz anecdote that sums up the differences between two distinct acting techniques, which I will call simply “method” and “not method”. In 1976, on the set of the spy thriller Marathon Man, Laurence Olivier and Dustin Hoffman, the film’s two stars, are apparently not getting along. Hoffman hasn’t slept for 72 hours in order to bring verisimilitude to his portrayal of a man being interrogated under sleep deprivation. Seeing his colleague turn up ragged before the cameras roll, Olivier drily remarks: “My dear boy, why don’t you just try acting?” There was an ocean between these method and not-method actors. Olivier, steeped in the worlds of the theatre and Shakespeare and classical poise; and Hoffman, no less a craftsman, but with his training grounded in realism and the “method”, as propounded by his teachers at the Actors Studio in New York. Lady Gaga, whose new film House of Gucci opens in the UK next week, appears to be from the Hoffman school. She recently revealed that playing Patrizia Reggiani, the Italian socialite convicted of hiring a hitman to assassinate her ex-husband, Maurizio Gucci, was a process of “becoming” rather than an “imitation”. She told Vogue that she stayed in character for 18 months, speaking with an accent for nine months of that. “Off camera,” she said. “I never broke. I stayed with her.” Jeremy Strong, too, has talked about the extreme toll that playing Kendall Roy has had on him in Succession. He says acting is “not just an imaginary experience” but “you go through something and […] it costs you”. His co-star Brian Cox has said it is torturous to watch. “Sometimes you say: ‘Jeremy, for [expletive] sake. Stop it now.’” The difference between these two approaches – the Hoffman and the Olivier – lies in what goes into a performance to make it believable. Olivier would work from the outside in, using external influences to simulate emotion (he once supposedly said, “I just turn upstage and pull a nose hair out” when asked how to cry on stage). Method actors work from the inside out in a relentless search for the “truth” of the character, learning everything they can about them and attempting to embody that information with every fibre. The practice of “staying in character”, during rehearsals, between takes and on and off set brings, they feel, authenticity to the performance – but it can be extreme. Film and television history is filled with stories of actors taking the method to extremes: Sylvester Stallone ending up in intensive care for eight days after wanting to be knocked unconscious by a co-star in Rocky IV. Nicolas Cage spending five whole weeks with his face covered in bandages and having his teeth pulled out for Birdy. Daniel Day-Lewis – one of the modern masters of the method – catching pneumonia while walking around New York without a proper coat when preparing for his role in Gangs of New York, or spending the entire filming period for My Left Foot in a wheelchair, being fed by crew members. Halle Berry not showering for eight weeks while filming Jungle Fever. And Jamie Foxx having his eyelids glued shut to play blind musician Ray Charles. The closest I have witnessed such transformative behaviour was in working with Joaquin Phoenix on the 2018 western The Sisters Brothers. In pre-production, our relationship was cordial. The moment the cameras started rolling, however, he became brooding, taciturn even, disappearing into the role of Charlie Sisters – we spoke little except for when performing scenes together (though he was a generous and accommodating scene partner, no Hollywood diva). A year later, when we were at the Toronto international film festival to promote the film, Joaquin was already in prep for his role as Arthur Fleck in Joker, and his weight loss and haphazard behaviour was disturbing – sitting in a crowded room with headphones on, only answering questions in monosyllables. Authenticity delights audiences. But where does it end? If you’re playing Macbeth, must you commit regicide? If you’re performing Romeo do you have to fall in love with the actor playing Juliet (and do you even have to fancy her)? Well, no. Yet while all acting is a form of pretence, you should have a sense of what that person could be like “in real life”. For me, and most actors I know, doing background research is an essential part of “finding a character”. We study the character’s education and social experience, their likes, dislikes and places they have lived. How they speak, and so on. What we can’t discover, we simply invent: the imagination is as powerful a muscle as biceps, glutes or abdominals for an actor. But clearly the method works. For many who adhere to it, glory at the Oscars seems inevitable; Joaquin’s performance in Joker won him an Academy Award. Maybe that’s why it remains the most esoteric and mysterious of acting techniques: it produces such endlessly startling, award-winning results, I’m tempted to try it myself. Rebecca Root is an actor. Her recent work includes The Queen’s Gambit