You've probably heard of the fight or flight response, but a few others Fs are often cited as common responses to threat: freeze, a la deer-in-the-headlights; fright, a.k.a. “playing possum“; and friend (also sometimes flirt or fawn), as in trying your darndest to engage and de-escalate the threat. Taken together, the Fs are sometimes referred to as the defense cascade model (although friend is often dropped).