The reciprocal relationship between speakers and audiences is well documented in rhetorical studies. The example of Hitler's development as a speaker is discussed in Ian Kershaw's biography "Hitler: 1889-1936 Hubris." According to historical accounts, Hitler's early speeches in 1919-1920 for the German Workers' Party were rather technical, focusing on economic topics like inflation and the Versailles Treaty's economic impact. Through audience reactions, he learned which themes resonated most strongly and adapted his rhetoric accordingly. His latter speeches focused on topics like nationalism, anti-semitism, anti-marxism, etc... topics far more popular with his audience.