The concept of “left brain” originates in an ancient view of the brain being divided into halves, with the left side associated with the rational and analytical processes, and the right side said to be associated with more intuitive and resourceful processes. Left brain functions such as language, logic, numbers and reasoning are seen as sequentially linear and focused on comparison, division and categorisation; the right side is thought to be engaged in more holistic, spontaneous and less linear mental activities. Thus, left brain activities are referred to as those involving conscious, linear, systematic and logical information processing.

See also: left hemisphere, right hemisphere, corpus callosum, split brain, hemispheric hypothesis