People with persistent predatory personalities cause an inordinate amount of pain. Recently, our shared understanding of them has grown – and it could help protect us

The classic checklist for psychopathy was developed in 1980 by Prof Robert Hare, who is still the recognised giant of the territory. The 20 traits, which ranged from pathological lying to a lack of empathy, were based entirely on prison populations. This worked because not only did Hare have the benefit of a large sample, with pronounced psychopathic behaviours, but he was able to compare interviews and self-reporting with data collected about the individuals – so inconsistencies could be identified.

However, Hare knew this approach was limited. In 1976, he said that he simply didn’t know to what extent his results could be generalised to non-incarcerated psychopaths, including female ones. “Research into the socially successful psychopath is badly needed,” he concluded. Even decades later in the early 2000s, when Hare wanted to look into psychopaths in politics, he still needed to go to prison to find them (Pinochet’s henchmen in Chilean jails). Research into the higher-functioning psychopath – who doesn’t get caught, or maybe doesn’t even resort to crime – has proved elusive, not least because self-reporting questionnaires don’t work. Psychopaths lie; arguably, that’s their main thing.