According to Sigmund Freud, primary process thinking is

The id is theorised to be the original state of human mental apparatus with which a newborn baby is born. It is totally unconscious, containing the basic drives and instincts concerned with survival, sexual drive and aggression. It is characterised by primary process thinking and is based on the pleasure principle, lacking any direct link with reality. The only urge of these drives is immediate gratification. Ref: A Sho Textbook of Psychiatry, Niraj Ahuja, 7th Edition, pg. no.206