When John Purnell’s 10-year-old son was diagnosed as autistic, he knew exactly how to respond. “I’ve always been fascinated by research, by detail, by finding out everything there is to find out about something,” he says. “So I did a really deep dive.” As he pored over academic papers and delved into medical science – including how many autistic people have a propensity and appetite for copious research – an unexpected realisation crept into his mind. “I was reading about the traits of an autistic person, the difficulties they often have in social situations, the need for order and planning:...