TORONTO—Attempting to understand the mind of an autistic person would be a challenge for anyone, but veteran actor Sigourney Weaver had to go one step further and inhabit that state of mind for five weeks. For her role in Snow Cake (which opens on Friday [December 15]), Weaver plays Linda Freeman, an autistic woman whose orderly, routine life is shaken like a snow globe when tragedy strikes her family and a mysterious stranger shows up at her door.

Sounds vaguely familiar, doesn’t it? But Weaver stresses that this movie is not Rain Woman. “What I liked about Linda’s situation is [that] unlike Rain Man, where the autistic character is taken out of his world, you get to enter Linda’s,” she says. “And you get to see that if she can set it up correctly, she can live by herself, she can have a job, and in many ways have a very normal life. There are certain things she can’t do, which you learn about, but there are other things that she can that we can’t.”

Weaver says she was deeply affected by the script, which was crafted by first-time screenwriter Angela Pell, who has an autistic son. “Angela wanted people to understand that living with someone with autism can be both heaven and hell,” Weaver says. “What makes me want to do a film is when it’s about much more than the people in it. This movie is a lighthearted look at some pretty dark things.”

Luckily, numerous delays in the film’s production schedule allowed Weaver extra time to prepare for the tricky role. “It took a lot of research,” she says. “I actually ended up working with some wonderful autistic people who taught me how to be autistic. Without the extra time, I think I’d have felt self-conscious doing the role, but by the time I had to do it, we’d been postponed so many times that I just sort of threw myself over the cliff and had autism for those five weeks.”

Today, Weaver looks downright glamorous in a smart brown silk blouse and high heels at the Toronto International Film Festival, where she’s promoting the film. She speaks about the experience of being autistic as a welcome change from her ?everyday life as a movie star.

Weaver says she entered the project with some preconceived notions about the nature of autism but she was quickly reeducated. “I thought I knew a little bit about autism, but it turned out I didn’t know anything,” she admits. “Now I do. The woman who helped me the most—Roz—was so incredibly generous. We had many, many laughs about me trying to be autistic. By the time I got to play Linda, I was really ready to go for it.”

What was the biggest revelation for Weaver? “Autistic people like who they are,” she says. “Every single person with autism I talked to told me that. It is hard, really hard sometimes; they need care, it’s very hard for them to find a good care person who they enjoy being with, who’s good at playing. But they do like who they are. They don’t want to be changed.

“I think I was sort of fortunate that I wasn’t playing the parent of someone autistic, which brings with it a whole set of challenges,” she adds. “Being a mother myself, I would be desperate for my daughter to have the basic tools to have her own independent life. But because I was playing someone with autism, I didn’t have any of those responsibilities or concerns, so I got to just come at it from their point of view, and that was very liberating.”

Weaver says that as an actor, inhabiting the role of someone like Linda is extremely difficult but enriching. “I mean, when do you get to use that part of yourself that loves to play and feels all that joy that we as adults don’t enjoy anymore? Playing is a serious game for them. It’s a full-time job. To be able to use all that and find out about yourself—to find the autistic person in myself was really incredible.”