The quirks in Ramsey Brewer’s conversation are subtle. The 17-year-old repeats himself from time to time and makes small mistakes in the words he uses. For instance, he says he and his best friend look scaringly, not scarily, similar. He also pauses at odd spots, and for a beat or two longer than most people do. When he’s talking, he makes eye contact briefly but then slides his eyes sideways — or closes them. And his comments swerve in unexpected directions: Asked where he goes to school, he says Boston Latin Academy, but then suddenly adds, “I’m not actually from this state,” even though he and his family have lived in Massachusetts for years.