In the United Kingdom, the use of improvisation was pioneered by Joan Littlewood from the 1930s onwards and, later, by Keith Johnstone and Clive Barker. In the United States, it was promoted by Viola Spolin, after working with Neva Boyd at a Hull House in Chicago, Illinois (Spolin was Boyd's student from 1924 to 1927). Like the British practitioners, Spolin felt that playing games was a useful means of training actors and helped to improve an actor's performance. With improvisation, she argued, people may find expressive freedom, since they do not know how an improvised situation will turn out. Improvisation demands an open mind in order to maintain spontaneity, rather than pre-planning a response. A character is created by the actor, often without reference to a dramatic text, and a drama is developed out of the spontaneous interactions with other actors. This approach to creating new drama has been developed most substantially by the British filmmaker Mike Leigh, in films such as "Secrets & Lies" (1996), "Vera Drake" (2004), "Another Year" (2010), and "Mr. Turner" (2014).