Automatic drawing 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 attibuted in part to the subconscious and may reveal something of the psyche, which would otherwise be repressed.
Automatic drawing was pioneered by André Masson. Artists who practised automatic drawing, include Joan Miró, Salvador Dalí, Jean Arp and André Breton. The technique 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.
Most of the surrealist's automatic drawings were illusionistic, or more precisely, they developed into such drawings when representational forms seemed to suggest themselves. A group of French-Canadian artists, les Automatistes, 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. (Romanian surrealists claimed to have taken this purity even farther with the development of what they called "surautomatic" methods, one of which is entopic graphomania, in which the impurities in the paper itself are supposed to define the drawing.)