In the early 1900s Walter Cannon formulated the phrase "fight or flight" to describe animal responses to a threat. Researchers have learned a lot since then but many people still use the outdated phrase, leading to faulty assumptions about animal behavior. These faulty assumptions could affect robotics researchers working on biologically inspired behaviors. H. Stefan Bracha argues that it's time to correct the popular phrase to something more like "Freeze, Flight, Fight, Fright, or Faint" (PDF format) which better represents the real world range and order of animal behavior. Freezing in the first repsonse to danger as the animal enters a hypervigilant state in which it becomes more alert and focuses on information gathering. Freezing is normally followed by an attempt to flee. If flight is impossible, the animal will then fall back on a fight response. If fighting fails, a fright response may result as the animal enters a state known as "tonic immobility" by ethnologists and "playing dead" by everyone else. In some mammals, such as Humans, a further evolutionary descendant of tonic immobility called fainting may occur.