what did joan miro believe the purpose of doodling was?

One year later, in “The Tilled Field,” the same elements – furrowed earth, vegetation, and barnyard animals – have been completely transformed into archetypal symbols. A tree magically sprouts an eye and ear, while fantastic animals cavort in antic extraterrestrial gaiety, like cartoons from another world.
His works alternate between an elaborate style, as densely figured as a Persian carpet, and loose, expansive spareness. As Miro put it, “We Catalans believe you must always plant your feet firmly on the ground if you want to be able to jump up in the air. The fact that I come down to earth from time to time makes it possible for me to jump all the higher.”

Visual artists in the Surrealism movement relied on drawing games and a variety of experimental techniques to randomize the creative process. For example, in a method known as decalcomania, artists splashed paint on to paper, then rubbed the surface to create patterns. Similarly, bulletism involved shooting ink onto a surface, and éclaboussure involved spattering liquid onto a painted surface that was then sponged. Odd and often humorous assemblages of found objects became a popular way to create juxtapositions that challenged preconceptions.
Art from the distant past can appear surreal to the modern eye. Dragons and demons populate ancient frescos and medieval triptychs. Italian Renaissance painter Giuseppe Arcimboldo (1527–1593) used trompe l’oeil effects (“fool the eye”) to depict human faces made of fruit, flowers, insects, or fish. The Netherlandish artist Hieronymus Bosch (c. 1450–1516) turned barnyard animals and household objects into terrifying monsters.

Surrealism was the first artistic movement to experiment with cinema in part because it offered more opportunity than theatre to create the bizarre or the unreal. The first film characterized as Surrealist was the 1924 Entr’acte, a 22-minute, silent film, written by Rene Clair and Francis Picabia, and directed by Clair. But, the most famous Surrealist filmmaker was of course Luis BuГ±uel. Working with DalГ­, BuГ±uel made the classic films Un Chien Andalou (1929) and L’Age d’Or (1930), both of which were characterized by narrative disjunction and their peculiar, sometimes disturbing imagery. In the 1930s Joseph Cornell produced surrealist films in the United States, such as Rose Hobart (1936). Salvador DalГ­ designed a dream sequence for Alfred Hitchcock’s Spellbound (1945).
Several Surrealists also relied heavily on automatism or automatic writing as a way to tap into the unconscious mind. Artists such as Joan MirГі and Max Ernst used various techniques to create unlikely and often outlandish imagery including collage, doodling, frottage, decalcomania, and grattage. Artists such as Hans Arp also created collages as stand-alone works.

References:

http://www.thoughtco.com/what-is-surrealism-183312
http://m.theartstory.org/movement/surrealism/history-and-concepts/
http://totallyhistory.com/joan-miro/