- "Triune" brain: each brain corresponds to a different stage of evolution
- Each brain is connected to the other two, but each operates indivually with a distinct "personality"
- Reptilian brain for instinctive behavior (brain stem, cerebellum, autonomic system)
- Old mammalian brain for emotions that are functional to survival, as in "avoiding pain and achieving pleasure" (limbic systemi, i.e. hippocampus, thalamus amygdala)
- New mammalian brain for higher cognitive functions (neo-cortex)
- Mechanical behavior, emotional behavior and rational behavior arose chronologically and now coexist and complement each other
- Jung's conscious, unconscious, collective unconscious