Automatic drawing was inspired by the automatic writing movement of the early 1900s, which is the suppression of conscious control, a noting of the conscious mind versus the unconscious mind.
Automatic drawing was pioneered by the English artist Austin Osman Spare who wrote a chapter, Automatic Drawing as a Means to Art, in his book, The Book of Pleasure (1913). Other artists who also practised automatic drawing were Hilma af Klint, André Masson, Joan Miró, Salvador Dalí, Jean Arp, André Breton and Freddy Flores Knistoff.
The technique of automatic drawing was transferred to painting (as seen in Miró's paintings which often started out as automatic drawings), and has been adapted to other media; there have even been automatic "drawings" in computer graphics. Pablo Picasso was also thought to have expressed a type of automatic drawing in his later work, and particularly in his etchings and lithographic suites of the 1960s.
Automatic drawing (distinguished from drawn expression of mediums) was developed by the surrealists, as a means of expressing the subconscious. In automatic drawing, the hand is allowed to move "randomly" across the paper. In applying chance and accident to mark-making, drawing is to a large extent freed of rational control. Hence the drawing produced may be attributed in part to the subconscious and may reveal something of the psyche, which would otherwise be repressed. Examples of automatic drawing were produced by mediums and practitioners of the psychic arts. It was thought by some Spiritualists to be a spirit control that was producing the drawing while physically taking control of the medium's body.
Most of the surrealists' automatic drawings were illusionistic, or more precisely, they developed into such drawings when representational forms seemed to suggest themselves. In the 1940s and 1950s the French-Canadian group called Les Automatistes pursued creative work (chiefly painting) based on surrealist principles. They abandoned any trace of representation in their use of automatic drawing. This is perhaps a more pure form of automatic drawing since it can be almost entirely involuntary – to develop a representational form requires the conscious mind to take over the process of drawing, unless it is entirely accidental and thus incidental. These artists, led by Paul-Émile Borduas, sought to proclaim an entity of universal values and ethics proclaimed in their manifesto Refus Global.
As alluded to above, surrealist artists often found that their use of "automatic drawing" was not entirely automatic, rather it involved some form of conscious intervention to make the image or painting visually acceptable or comprehensible, "...Masson admitted that his 'automatic' imagery involved a two-fold process of unconscious and conscious activity...."
Source (above): Wikipedia