The phenomenon of personality traits impacted by trauma to the brain is well-documented through history, dating to at least the late 18th century.
Consider the case of Phineas Gage: a New England railroad foreman who, in 1848, was working at a rock excavation site. With an iron rod, Gage was tamping gunpowder into a drilling hole. The force of the iron striking the pressurized gunpowder prompted a premature explosion, sending the iron rod through his left cheek and skull before tearing through a portion of the man's frontal lobe and protruding through the top of his skull.
Historical recollections of Gage depict the healthy 25-year-old as a "very good and hard worker. A family man," said Dr. Mark George, a Medical University Hospital-based neurologist and psychiatrist, who has spent nearly three decades studying human behavior through brain imaging.
A former Upstate police chief who was forced to resign and later went on to rob a Simpsonville bank was shot by a Lowcountry sheriff's deputy …
As documented in a case study published by the U.S. National Library of Medicine, Gage's doctor noted that, after his injury, he'd become "exceedingly capricious and childish, but with a will as indomitable as ever."
"His mind was radically changed," the doctor wrote. "So decidedly that his friends and acquaintances said he was ‘no longer Gage.'"
Speaking generally, George noted the parallels between Gage and Richard Inman — the small town police chief arrested for bank robbery years after brain surgery for a frontal lobe tumor. George said it's probable his behavior and personality could have been affected in a similar way.
"That's the problem with that part of the brain. It does stop us and stops impulsive behavior," he said. "The part of the brain that would normally be a brake is just not there."