Dustin Hoffman's portrayal of autism in "Rain Man" 18 years ago has been considered definitive, but only about one in 200 autistic people are savants -- people with extraordinary talents in music and math, for example, The Independent reported.
In "Snowcake," Sigourney Weaver, 56, plays an autistic woman, Linda, who lives alone and holds a job. She is not savant, but has trouble understanding social rules.
Alan Rickman plays a man who gives Linda's daughter a lift when she is hitchhiking. After a truck hits his car, killing the teen, he meets Linda and becomes involved in her life.
Weaver said she hoped the movie might challenge people's expectations.
Carol Povey, the head of adult services for Britain's National Autistic Society, said her organization welcomed the movie.
"We think it's great to have as many portrayals as possible of individuals with autism in all sorts of media," Povey said.