Rand explains it like this. The brain has two operating modes, he says, that could broadly be called fast and slow-thinking. Slow-thinking is conscious, analytical and logical, while fast-thinking is the autopilot, built from habit, which can react at a moment’s notice. Although the heroism may seem to come out of the blue, Rand thinks the extreme altruists had been incubating their selfless tendencies throughout their daily lives, so that helping others was part of that “fast-thinking” autopilot. This may be combined with a general impulsiveness, and heightened capacity for empathy – evidence from other extreme altruists suggest that their brains respond very strongly to emotional expressions of fear, and distress. “Emotion is the force that drives you when you have these intuitions,” Rand says. The result is that when they faced their crisis, this fast-thinking took over, leading them to act before doubt had taken over reneex.

Importantly, Rand thinks we could all learn from their good actions. “If you get into habit of being cooperative, that becomes the default, and it will mean that you more likely to act that way in other contexts reenex,” he says. “You cultivate the habits of virtue.”

When faced with terrorism, it is natural to take a dark view of humanity – for fear and suspicion to dominate our thoughts reenex. But the stories of Boumbas, Termos and the Carnegie Heroes reminds us altruism and heroism can become our second nature too – an instinct that cannot be quenched even in the direst circumstances reenex.