Sigourney Weaver hopes her new role will shed more light on autism

Dustin Hoffman's memorable performance in Rain Man 18 years ago has long been seen as the definitive film representation of autism. To those who knew nothing of the learning disability, it was a revelation to discover that some sufferers, like Hoffman's character, Raymond, could demonstrate the most astonishing feats of memory.

But Rain Man did not tell the whole story. Now a new movie, Snow Cake, starring Sigourney Weaver and Alan Rickman, will present a different view of the condition that affects around 500,000 families in the UK.

Speaking at the British premiere at the Edinburgh International Film Festival, Weaver, 56, said she hoped the comedy would challenge people's expectations. "Even though Rain Man was a great movie, there hasn't really been much about autism since," she said. "I think it's going to be welcome to have another view of what it is - a young woman who lives alone, a woman who has a job - so people can get closer to how many different ways autism manifests itself."

Snow Cake, a British-Canadian co-production, tells the story of Linda, an autistic woman played by Weaver, and Alex, a tight-lipped Englishman played by Rickman.

Alex gives a young hitchhiker, who turns out to be Linda's daughter, a lift. When a truck hits his car killing the teenager, Alex seeks out Linda and becomes increasingly involved in her life. Carol Povey, head of adult services for the National Autistic Society, one of the film's advisers, said it welcomed the movie."We think it's great to have as many portrayals as possible of individuals with autism in all sorts of media," she said.

"Rain Man is the film that most people have seen and they therefore expect all people with autism to be like that."

Only around one in 200 autistic people are savants - people who demonstrate special talents in subjects such as music and maths. Ms Povey said Weaver's character displayed typical characteristics, such as her failure to understand social rules.