It's based on anecdotes from others and a lifetime of observation.
"Probably."Steve Martin is notoriously uncomfortable in interviews and intensely dislikes talking about himself, so it is nothing short of extraordinary for him to be discussing, albeit reluctantly, past love affairs and emotional milestones in his life.
But there are certain things that have to be done even if you're a celebrated actor, comedian, screenwriter, producer, playwright and author, and Martin knows that if he wants Shopgirl to be noticed he has to put on a brave face and courteously answer questions he would far rather ignore.
It is difficult to reconcile the quietly spoken, sophisticated, 60-year-old actor-writer with the hyperkinetic comedian who won laughs by sporting a fake arrow through his head and coining the catchphrase, "Well, excuuuuse me!
" His home is now a rambling ranch-style home in the Hollywood Hills, where he keeps his extensive art collection and works at his other profession as a writer.
Love is a test."I've been through many stages in my life, and certainly one stage was like Ray Porter - being emotionally unavailable and afraid of intimacy. I was essentially on the road from age 25 until I was 40, and it's a very, very lonely life.
You're in a town for one or two days and you're always packing a suitcase and you sort of adapt to that kind of life."Mirabelle is a pastiche of people I've known; and when you live in Los Angeles you drive around and you look at all these shop girls and kind of fantasise about their lives."Has he had an affair with a shop girl?
"They worked hard to have the baby." Martin's rep could not be reached for comment.
Steve Martin is reminiscing about a long-past love affair.
It happened, he says wryly, "when I was still a celebrity", and he and the woman talked about it later.
"I asked her why she had slept with me, and she said, 'So I can tell my friends,'" he says with a smile, although he does not seem very amused.
"Everybody has their own taste and what makes it all go round is there's somebody for everybody.