Paul MacLean formulated the triune brain model in the 1960s and expanded it in his 1990 book The Triune Brain in Evolution. The model proposed that the vertebrate forebrain evolved in three successive layers, each adding a new kind of behavior on top of the last, and became widely popular in both psychology and popular science for decades.
Facts
Debunked
Core ClaimThe vertebrate forebrain evolved in three distinct layers, a reptilian complex governing instinct, a paleomammalian limbic system governing emotion, and a neomammalian neocortex enabling rational thought, each an evolutionary addition on top of the last. 1 Comparative neuroscience considers the model outdated: the brain structures MacLean treated as unique to each evolutionary stage are now known to appear across many vertebrate groups, including reptiles, which show cognitive abilities the model did not predict; the article states the hypothesis is now regarded as a myth, largely abandoned by comparative neuroscientists around the turn of the twenty-first century. Connections
Sources
1. Wikipedia: Triune Brain
Wikimedia FoundationModern assessmentQuote, Modern assessment
Since the 1970s, the concept of the triune brain has been subject to criticism in evolutionary and developmental neuroscience and is now regarded as a myth.
Dissenting Readings (1 dissenting reading)
Core Claim
Human brain evolution researcher Terrence Deacon holds that later findings have refined the neuroanatomical ideas MacLean based the triune brain hypothesis on, undercutting the model's premise of three cleanly layered, sequentially added brain regions.
A dissenting reading, from Terrence DeaconWikipedia: Triune Brain, Wikimedia Foundation
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