Abstract

Unconscious processes are mental states that occur in the absence of subjective awareness. We offer a focused historical survey of the robust debate about the nature of unconscious mental processing, from ancient and medieval theories that allow for bodily functions without subjective awareness to the 20th century acceptance of autonomous unconscious processing. The background introduction culminates with the rise of cognitive science in the latter half of the 20th century, as dual systems theories claimed that the mind had two forms of processing: an unconscious system that is associative, fast, and automatic and a conscious system that performs sequential, deliberative, and slow mental functions. More recently, the “cognitive unconscious” has been discovered to perform most if not all cognitive functions including higher-level cognitive processing, such as addition and subtraction. Despite a rich history of experimental methods and findings, recent criticisms are forcing scientists to reexamine these advancements. We are optimistic that the field will develop novel techniques that answer these criticisms, including measures for studying subjective reports in the absence of subjective awareness of the content of the unconscious state and the act of reporting.