It was just after three o'clock and the shopping centre was teeming with people. Suddenly, screams filled the air: a man with a knife was on the rampage. But while most people made for the exits or barricaded themselves in shops, a police officer raced to confront the attacker.  

By the time Inspector Amy Scott reached the mall, the knifeman - later identified as Joel Cauchi - had killed six people and wounded twelve others.

The armed policewoman tracked him to the fifth floor and shouted "Put it down!" Instead, he raised his knife; Scott shot him, and he fell to the ground.

Australia's prime minister, Anthony Albanese, described Scott as a hero. The incident, he said, was "a reminder that those people who wear uniform are people who rush to danger, not away from it".¹

Yet Scott was not the only person who showed enormous courage. Some of the shoppers knelt to help the wounded instead of seeking safety. One man, Damien Guerot, confronted Cauchi armed only with a pole. 

Heroes can take unexpected forms. Roy Larner, who has criminal convictions for assault and possessing drugs, is a case in point.

In 2017, when three terrorists armed with 12-inch knives attacked people on London Bridge and in Borough Market, Larner took them on barehanded. He received multiple stab wounds and almost died as a result - but his bravery bought precious time for those fleeing the scene.

This week a six-year-old girl from Yorkshire was also hailed as a hero. Olivia Patterson was playing outside when she saw flames rising from the roof of her house. Olivia ran into the burning building to wake her mother, who was asleep on the sofa with her two younger children.

According to one psychiatristA doctor who specialises in diagnosing and treating mental illnesses. , Professor Deane Aikins, some people are physically prepared for heroism. They feel fear but do not show signs of panic.

While most of us are overwhelmed by a stress hormoneChemicals carried in the bloodstream that alter the way your body's systems act.  in dangerous situations, they experience lower levels of it - and are actually calmed down by another one. He cites as an example Chesley Sullenberger, a pilot who safely landed an airliner on the River HudsonA river that flows through New York. after both its engines failed. 

Another psychologist, Dr Punit Shah, argues that people who "act quickly and are more impulsiveActing without thinking much about it. are more likely to engage in acts of heroism... people that are risk-takers".²

Is courage a little bit mad?

Yes: Human beings have evolved successfully because they have strong survival instincts, which means avoiding danger rather than confronting it. Those who put themselves at risk must be slightly crazy.

No: There was nothing mad about Amy Scott's actions. As Professor Aikins testifies, heroism consists of keeping a cool head and not panicking, which means that it is the very opposite of madness.  

Or... Everyone is different, so it is impossible to generalise. It is probable that Amy Scott acted out of a sense of duty, Olivia Patterson out of concern for her family and Roy Larner out of anger.