Harvard neuroscientist Dr. Jill Bolte Taylor reveals how your brain contains four distinct personalities—two emotional systems and two thinking systems—one in each hemisphere. Understanding how to switch between them can help you manage trauma, addiction, emotional reactivity, and achieve greater calm, focus, and peace in daily life. Your brain contains four personalities: left-thinking (analytical), left-emotional (holds past pain), right-emotional (present-moment play), and right-thinking (wisdom/peace)—and trauma and addiction live in the left hemisphere's emotional system.