Book excerpt: Psychiatry has ignored the normal. The focus on defining abnormal behavior has obscured what turns out to be a more fundamental question—how does the biology of the brain give rise to the mind, which in turn gives rise to everything we care about: thoughts, feelings, desires, and relationships? In The Other Side of Normal, Harvard psychiatrist Jordan Smoller shows us that understanding what the mind was designed to do in the first place demystifies mental illness and builds a new foundation for defining psychiatric disorders—from autism to depression. Smoller argues there are no bright lines between normal and abnormal. Psychiatric disorders are variations of the same brain systems that evolved to help us solve the challenges of everyday life. How do we become who we are? Smoller explains where our personalities come from, and how the temperaments we had as infants actually stay with us into adulthood. Why do we choose to date, love, and marry the people we do? Why do some of us form healthy relationships while others form unstable ones? Our relationships are shaped by the biology that drives two imperatives: maternal-child bonding and child-parent attachment. Along the way, Smoller tackles an even greater question—what do we mean by "normal"?—as he explores the puzzles behind the epidemics of multiple personalities and koro, the shocking phobia that one's penis is shrinking. He also looks at the controversial history of psychiatric classification and the explosive debates over how much early experiences influence our minds and to what degree genetics affect our temperaments, personalities, and emotional lives. Throughout this examination, Smoller explores the hidden sides of such questions as: How are trust and love rooted in biology? How much does sexual attraction stem from biology rather than culture? And what can the scientific study of normal behavior tell us about what it means to be human? Based on the author's groundbreaking research and personal experiences treating psychological disorders, The Other Side of Normal changes the way we think about the human condition.