Automatic writing is the ability to write without conscious thought. Some believe that it is a psychic ability – one that stems from a spiritual or supernatural source and many books have supposedly been written via channeled sources. One of the most popular of these authors is Jane Roberts, an American author, poet, self-proclaimed psychic and spirit medium who claimed to channel an energetic personality who called himself “Seth”.
“Automatic writing has been used as a tool in Freudian psychoanalysis and in related “self-knowledge” studies, where it is seen as a means of gaining insight into the mind of the automatic writer through their subconscious word choices.” – New World Encyclopedia
The Surrealist artists of the 1920s borrowed many of the same techniques from Freud and other psychoanalysts to stimulate their writing and art. These artists believed that creativity from the subconscious could be more powerful and authentic than any derived from conscious thought. As automatic writing was a popular game among the surrealists, so was automatic drawing. The surrealists would write or draw as quickly as possible, attempting to remove conscious control over what was being written or drawn.
Read more about Surrealism at Wiki and at MoMA Learning, Read up on Automatic Writing at New World Encyclopedia and at CrystalLinks and Automatism at Encyclopedia Britannica and here is a How To on Automatic Writing from Anna Sayce.