Jessica Chastain was in such a flow state while filming Michel Franco’s new dementia drama Memory that she didn’t remember all of the acting choices she’d made until she watched the movie back for the first time.

Jessica Chastain on Memory

“Because I think I had worked on it, I didn’t realize how it physicalized in my body until after I saw the movie,” Chastain said during a Q&A with Franco and her co-star Peter Sarsgaard at the Santa Barbara International Film Festival.

In Memory, Chastain plays a social worker named Sylvia whose very structured life revolves around her daughter, her sobriety meetings, and her work. But all that is disrupted when Saul (Sarsgaard) follows her home from their high school reunion. Realizing that Saul has dementia, Sylvia becomes his caretaker despite her own dark memory of him from the past.

Chastain explained how her acting choices became so second nature to her that she wasn’t even aware of everything she was doing with her body until she watched the scenes later.

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“I spent so much time before we got on set understanding what her life was,” Chastain said. “I would never mention it to Peter’s character — we never talked about it — but I had to know things like how her daughter was conceived. Did she even know how her daughter was conceived? What was her lowest day before she decided to get sober? What did her father smell like? What movie would be playing on TV? All of these things that would be so real for her. And then by the time I got on set, I never thought about it again, because she wouldn’t be walking into a room thinking about it.”

Her character’s backstory became so ingrained in her that she began to make physical acting choices that she wasn’t even aware of in the moment.

“Because I think I had worked on it, I didn’t realize how it physicalized in my body until after I saw the movie. I didn’t realize — like in the the intimate scene when they’re together — I didn’t make a choice to blink so much or to have these things,” she said. “Then when I saw the scene, I was like, ‘Oh, wow.’ I think there’s something that happens. It changes from film to film, but it’s like the character grows inside you, and she grew inside me. It’s like she takes over and I’ve not even really sometimes aware of what’s happening.”

Watch the full Q&A below.

Memory arrives in select theaters in the U.S. on Dec. 22.

Main Image: Jessica Chastain, Peter Sarsgaard and Michel Franco courtesy of SBIFF