MacLean’s Triune Brain Concept: In Praise and Appraisal

Abstract

Paul D. MacLean is a pioneer, a trailblazer, a scientist, and thinker well ahead of his time. As a humanist deeply interested in the larger questions of human life, he started out studying philosophy. Unable to find satisfactory answers to questions such as the origin and meaning of life...why humans in spite of their unrivaled intelligence, often behaved in seemingly irrational ways threatening their individual as well as species survival...he turned to medicine and the study of the human brain. He anticipated that the brain, as the biological substrate of these behaviors, held the key to better understanding of these fundamental questions as well as hopefully their answers. MacLean was, for many years, chief of the Laboratory of Brain Evolution and Behavior of the National Institute of Mental Health. In 1952, drawing upon the nineteenth century French scientist, Paul Broca’s designation of the great limbic node which surrounded the brainstem of mammals, he introduced the conceptual term limbic system into the neuroscientific literature. In 1970 he introduced the concept of the triune brain, which became widely popularized after the publication of Carl Sagan’s rather overly dramatic and simplified discussion of it in The Dragons of Eden (1977). MacLean, in further developing the triune brain concept, which aroused great interest in psychiatry, education, and the lay public, produced his detailed and highly documented volume, The Triune Brain in Evolution: Role in Paleocerebral Functions in 1990.