Jane Addams was awarded the Nobel Peace Prize in 1931 for her work leading the Women's International League for Peace and Freedom. Sinclair Lewis won the Nobel Prize in Literature in 1930 for his realistic portrayals of characters and ability to use humor. In 1936, Carl D. Anderson won the Nobel Prize in Physics for his discovery of the positron in 1932. Harold C. Urey won the Nobel Prize in Chemistry in 1934 for his discovery of heavy hydrogen.