In new movie Her, Joaquin Phoenix plays a lonely writer who falls in love with a computer operating system that has the voice of Scarlet Johansson. Called Samantha, the AI and speech technology of this personal assistant is far more advanced than anything currently available, but how close is it to becoming reality? Could a computer's intelligence and speech one day become so life-like that we could fall in love with a machine?

Footage from Her courtesy of Warner Bros/Entertainment Film.