We explored the famous—and mistaken—triune brain model that neuroscientist Paul MacLean began developing nearly 80 years ago. How the lizard brain myth grewMany college-level textbooks—and specifically, many Psychology 101 textbooks—referred to the triune brain as a real model until at least 2017. This makes sense if their creators studied the triune brain model in college and were graded on their knowledge of it. Tracking the lizard in the modern dayBecause the triune brain model has been around for so long, its disconfirmed ideas have taken on a life of their own. If you hear people talking about their lizard brains or emotional brains, or that they're "acting from their amygdala," or that they need to "regulate their nervous system," they're calling back to the triune brain model.