same time, Francis Picabia and Marcel Duchamp were exploring similar notions. At a 1917 art show in New York, Duchamp presented a white porcelain urinal (Fountain) signed R. Mutt as work of art, becoming the father of the readymade. When Dada reached Paris, it was avidly embraced by a group of young artists and writers who were fascinated with the writings of Sigmund Freud, particularly by his notion of the unconscious mind. The provocative spirit of Dada became linked to the exploration of the unconscious mind through the use of automatic writing, chance operations, and, in some cases, altered states. The surrealists quickly turned to painting and sculpture. The shock of unexpected elements, the use of Frottage, collage, and decalcomania, the rendering of mysterious landscapes and dreamed images were to become the key techniques through the rest of the 1930s. Immediately after this war the French art scene diverged roughly in two directions. There were those who continued in the artistic experiments from before the war, especially surrealism, and others who adopted the new Abstract Expressionism and action painting from New York, executing them in a French manner using Tachism or L'art informel. Parallel to both of these tendencies, Jean Dubuffet dominated the early post-war years while exploring childlike drawings, graffiti, and cartoons in a variety of media. The late 1950s and early 1960s in France saw art forms that might be considered Pop Art. Yves Klein had attractive nude women roll around in blue paint and throw themselves at canvases. Victor Vasarely invented Op-Art by designing sophisticated optical patterns. Artists of the Fluxus movement such as Ben Vautier incorporated graffiti and found objects into their work. Niki de Saint Phalle created bloated and vibrant plastic figures. Arman gathered together found objects in boxed or resin-coated assemblages, and César Baldaccini produced a series of large compressed object-sculptures. César Baldaccini was a prominent French sculptor of the 1960s, who created large waste sculptures by compressing discarded materials like automobiles, metal, rubbish, and domestic objects. In May 1968, the radical youth movement, through their atelier populaire, produced a great deal of poster-art protesting the moribund policies of president Charles de Gaulle. Many contemporary artists continue to be haunted by the horrors of the Second World War and the specter of the Holocaust. Christian Boltanski's harrowing installations of the lost and the anonymous are particularly powerful. French and Western Art museums of France