Book excerpt: Challenging our understanding of what it means to be human, Joel Salinas, a Harvard-trained researcher and neurologist at Massachusetts General, shares his experiences with mirror-touch synesthesia, a rare and only recently identified neurological trait that causes him to feel the emotional and physical experiences of other people. Performing a spinal tap, he feels the needle slowly enter his lower back. If a disoriented patient flies into a confused rage, Salinas slips into a similarly agitated physical state, and when a patient dies, he experiences an involuntary ruin—his body starts to feel vacant and lifeless, like a limp balloon. Susceptible to the pain and discomfort of his patients, most of whom suffer from a host of disorders and extreme injuries, Salinas uses his trait to treat their symptoms, almost as if they were his own. At the same time, in his personal life, his mirror touch blurs the boundaries between himself and those close to him until he ends up inextricably entangled, no longer able to differentiate where he ends and someone else begins. Salinas refers to his condition as a kind of compulsory mindfulness, a heightened empathic ability that offers him invaluable clues about how to see and live the world through other people’s perspectives. This heightened sense of awareness is at the center of Mirror Touch. Through his experiences, both in his neurological practice and his personal life, Salinas offers readers insights about mirror-touch synesthesia and how the brain, in its endless wonder, can sometimes perform in a nearly superhuman, extrasensory way. In the process, Salinas reveals the full power and potential of his trait, as well as its thorny complications and often debilitating limitations. Beautifully written with intelligence and compassion and anchored by the latest developments in neurology, psychology, and psychiatry, Mirror Touch is an enthralling and wholly original investigation into the unexplored corners of the brain, where the foundation of human experience and relationships take root—everything it means to think, to feel, and to be.