The year was 1877. Dr. Joseph Bell, a brilliant surgeon and lecturer at Scotland’s prestigious Edinburgh University Medical School, was standing next to one of the hospital’s patients. His students – including 18-year-old named Arthur Conan Doyle – stood around him as he motioned to the patient and systematically ticked off his first observation about the case. “You’ll notice, gentlemen,” Dr. Bell began, “that the man is clearly a left-handed cobbler.” How could Dr. Bell tell a man’s occupation – and the fact that he was left-handed – from a single glance at someone he had never met before? Doyle and the rest of the students were amazed.