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It's been claimed on psy SE that are five common fear responses Fight, Flight, Freeze, Fawn, and Faint (or maybe fright, flight, fight, freeze, fawn as in a post further linked from there).

To me this classification doesn't seem well supported by animal experiments... (The poster is a certified psychologist, however). Do biologists agree with a 5F classification of fear responses?

And to make this less of a yes/no question: do biologists (commonly) classify fear responses in a more fine-grained manner (than the simple fight v flight paradigm)?

It seems to me that the 3F classification fight-flight-freeze (which seems more widely endorsed even in psychology than the 5F) has a reasonable correspondent in animal behavior. But I haven't found much biological literature discussing it as such... although it presented as such in a news/pospsci video-article in Nature. The actual paper that that video is about, presents a somewhat different 4-way nested classification :

Adaptive behavioural responses to visual threats fall into two general categories: those that reduce saliency to predators (to avoid detection), such as freezing or hiding, and those that enhance saliency (to avoid capture), such as fleeing or retaliatory aggression.

N.B., one of the review papers cited by that one does use the 3F though:

Freezing, fleeing or fighting back are general defensive responses in many taxa. These defenses are mutually exclusive, since a prey cannot simultaneously flee and fight, or freeze and flee. Each of these defenses by itself is rudimentary and probably cannot provide a completely effective means to elude predation. Freezing is efficient only if employed before the prey is spotted by the predator, otherwise the prey becomes a stationary, easy to catch target. In fleeing, the prey can move directly away and maximize its distance from the predator, move toward the predator to confine it to a single clashing point, or dodge sideways to evade the attack. Prey can also run in a straight path that is efficient against slow or distant predators, or in a zigzag path that is efficient when a raptor is close or fast. In all, freezing and fleeing constitute together a complex and flexible defensive response, and are probably controlled by different motor systems that are interconnected to allow fast switching between these behaviors, as required for an effective and versatile response.

So is there a commonly agreed classification in biology for fear responses?


After thinking a bit more about this, it's probably reasonable enough to consider "fawning", that is submissive behavior as an alternative response, with the caveat that it doesn't show up much in predator-prey contexts, but mainly in contests between sexes (usually males) of the same species. I don't know if biologists see it this way though... i.e. as related to the other responses.

And if that's not complicated enough, one author suggests "risk assessment" (behavior) as a separate part of the response repertoire (in predator-prey interactions):

In rodents, an extensive repertoire of innate defensive behaviors can be seen in predator-prey interactions in natural and semi-natural (laboratory) situations. To predator threat, rodents of small prey species exhibit a general cessation of ongoing non-defensive activities (e.g., grooming, playing, foraging, feeding and sexual behavior) in both adults (Blanchard and Blanchard, 1989) and preweanling pups (Takahashi, 1992), along with enhancement of avoidance, flight, freezing, risk assessment, defensive threat and defensive attack behaviors (Blanchard and Blanchard, 2008). Rodents will also readily bury novel, aversive, or potentially dangerous objects (Treit et al., 1981). Manifestation of specific behaviors is dependent on a number of factors: (1) context – an animal will typically flee a threat within an environment in which escape is possible, yet when trapped it will freeze; (2) stimulus ambiguity – whereas ambiguous stimuli, such as predator odors, elicit risk assessment behaviors (e.g., stretch attend, stretch approach, olfactory investigation) and are often associated with a state of anxiety, discrete, present threats elicit flight, avoidance, defensive threat and attack, and are associated with a state of fear; (3) defensive distance – the distance between predator and prey shifts defensive coping strategies from avoidance to escape, with short distances to the threat and unavoidable contact culminating in defensive threat and attack postures.

This last quote highlights something else I've been pondering, namely the difficulty in delineating fear from anxiety in animals. Depending where one draws the line between these, more or fewer responses qualify for a classification...

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  • $\begingroup$ To add to the discussion, there is talk of a 6th response. This is a newspaper article. I will try and find the clinical psychologist's report, but may be next week before I find it $\endgroup$ – Chris Rogers Apr 26 at 12:23
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    $\begingroup$ I've never heard "5F" referred to in animal behavior; this seems a bit opinion-based, though, is it not? Sort of a lumpers-vs-splitters argument. As far as fear vs anxiety, that's somewhat of a separate issue, although it is certainly of great interest especially in designing rodent experiments to apply to human psychology. From a neuroscientific perspective, though, I think fear and anxiety in rodents are considered to have the same responses, the fear vs anxiety distinction is more about context and higher order processing. $\endgroup$ – Bryan Krause Apr 26 at 20:54

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