Your Brain Is Not an Onion With a Tiny Reptile Inside

triune-brain theory: idea that "new" lobes are built on top of old ones.

14 of 20 introductory psychology textbooks sampled teach the triune-brain theory model.

Instead, the correct view of evolution is that animals radiated from common ancestors (Fig. 1c). Within these radiations, complex nervous systems and sophisticated cognitive abilities evolved independently many times.

Along with this misunderstanding comes the incorrect belief that adding complex neural structures allows increased behavioral complexity—that structural complexity endows functional complexity.

The idea that larger brains can be equated with increased behavioral complexity is highly debatable (Chittka & Niven, 2009).

At the very least, nonhuman animals do not respond inflexibly to a given stimulus. All vertebrate behavior is generated by similar neural substrates that integrate information to produce behavior on the basis of evolved decision-making circuits (Berridge, 2003).

Instead, much evolutionary change consists of transforming existing parts.