In a now famous study, Coan wondered how the presence of loved ones might alter the brain’s response to threatening situations. To introduce threat, he used a threat-of-shock paradigm. While the participants lay in the neuroimaging scanner, they viewed a series of Xs and Os on a screen. When a blue O appeared, they knew they were safe from shock. When a red X appeared, they knew there was a 20% chance of experiencing a slight electric shock to their ankle.