Aside from the famous six-day hostage situation at the Sveriges Kreditbanken in Stockholm from which its name is derived, Stockholm syndrome is perhaps most famously associated with the iconic photo of a beret-wearing, gun-toting Patty Hearst robbing a bank in April 1974. The story gripped the nation as the public questioned whether she was brainwashed or acting of her own accord. What turned the wealthy granddaughter of a media tycoon from an innocent hostage to a criminal, and seemingly willing, member of her captors’ radical Symbionese Liberation Army?

The term “Stockholm syndrome” was first coined by psychiatrist Nils Bejerot, who advised law enforcement during the Stockholm hostage negotiations in 1973. The public and the media were stunned by the hostages’ empathetic and defensive feelings toward their captors, and Bejerot labeled the psychological phenomenon “Stockholm syndrome.” It was defined in greater detail by Dr. Frank Ochberg in the 1970s as he studied the behavior of the Stockholm captives and identified the psychological factors contributing to their affectionate bonding with their captors.

Stockholm syndrome, also known as trauma bonding or terror bonding, is born out of the hostage’s instinctual sense of self-preservation: his basic survival is controlled by his captor, so rather than hate the captor, the hostage unconsciously forges a bond with him in order to survive. The hostage forges this bond by accepting and feeling gratitude for small acts of kindness from his captor; in the case of the Stockholm captives, they were given blankets when they were cold and were allowed to call their families. In the hostage’s world, the captor has become his provider, whereas the armed law enforcement team in the outside world poses a physical threat to both him and his provider.

The symptoms of Stockholm syndrome are not always clearly defined, and in Patty Hearst’s case, the jury’s doubts regarding the legitimacy of her psychological trauma resulted in a guilty verdict and a seven-year prison sentence, which was commuted two years later by President Carter.