There’s a bunch of different possible responses to fight or flight, there are lots of ways that it can go horribly wrong for the person who is experiencing it. Fight or flight is a natural instinctive response that is there to save your life, the problem is that instinct is a killer. Relying on your natural instincts will get your killed, I don’t really care if you’re a supernaturally endowed Vampire Slayer or an average person on the street. There’s a reason why martial combat involves retraining the instincts and, in most cases, outright replaces them with an entirely different set of responses is because the natural ones stink.
A lot of books try to cheat their way out of that with characters just “instinctively knowing” what to do because that’s easier for the author to use as opposed to crafting a character that can deal with the situation. Unfortunately, a character who is relying on their instincts is one that’s no longer rationally processing information and is running on their emotions, their fear and their terror. These emotions can be powerful tools, assuming the person is still in charge of their higher brain functions. If they’ve given in, then it can become deadly for them.
This rule is true even for trained martial artists. If you’ve been trained specifically to subvert an instinct, then you can take advantage of anyone who hasn’t been conditioned against that specific instinctual reaction. Starke did this to me when he showed me bursting (which is a technique common to Krav Maga where two strikes happen simultaneously instead of as a one and two in a combination), I’ve been trained to deal with one strike not two at the same time. So, I instinctively moved to block the one that came high, instead of the important one which was coming into my stomach. I’m trained to respond to any form of movement entering into my peripheral vision, but not to look for two strikes at the same time. So, I’ll respond to the one I see first. This won’t actually work against someone who is untrained, because the attack is betting on a very specific kind of response from a trained combatant.
Combat works by being one step ahead of where someone else’s training already is and it takes work to stay ahead of the curve. Not to bash on Joss Whedon and Buffy too hard, but the sad truth is, if the show played out under real world rules, that Buffy could be taken down by any decent martial artist. She has an over reliance on her own instincts and acts with the expectation that she’ll naturally know what to do instead of working under the assumption that she has to train to stay one step ahead of the competition. Forget about other characters with superpowers, Buffy could be taken out by Mulder from the X-files and he routinely gets his ass handed to him by characters with more combat training throughout the show’s run.
Some common reactions to fight or flight:
Freezing up. It’s common for someone to go with neither fight or flight, instead they get stuck between the two. Their brain is pulling them in two different directions and the end result is that they do nothing at all.
Running away. This is the flight response. However, the problem with the flight response is that the person in question is not necessarily in control of which way that they are running away. They’re just trying to flee. Instead of taking inventory of their surroundings and choosing the best route that will lead them away from danger, the individual in question has about a 50/50 chance of ending up in a situation that’s worse than the one they were in before. This could involve fleeing into a dead end alley, not running far enough away, not taking cover if the person who is chasing them has a gun, or turning around and fleeing into the arms of a secondary captor. They’re just running, that’s it. Running without purpose or thought. This will also not stop the person who initially triggered this response from chasing them. At that point, it’s a question of who has the better athletic ability and who is running with their brain turned on. It’s hard to get away if you’re not thinking about where you’re going.
Fighting back. Then, there’s the fight response. It’s worth noting that just because someone responds by fighting that doesn’t mean that they’re actually going to be any good at it. They could be powered by a lot of things, anger, rage, adrenaline. But, here’s the issue: fighting on anger alone is fighting stupid. People who fight on anger forget that they can be hurt and they become reckless. If the initial aggressor has kept their cool then they are the ones that are actually in control of the fight. Sometimes, pain is enough to knock someone back into reality and that’s when fear takes over again. Then, the fight stops, the person who acted on instinct loses their steam, and they lose.
The Fugue State. We make a big deal about fugue states and berserkers, but the problem with a fugue state is that the person in it is still only acting on anger and rage. The fugue state does not endow them with any more skill then they previously had and they are in even less control of their body than the person who just acted on the anger response. If the person in the fugue state has blacked out, then all they are doing is acting on instinct alone and while they may not notice the fact that they’ve been hurt they’re even more vulnerable to an aggressor who can manipulate someone’s instinctive reactions to their benefit. If the fugue state fails to scare the aggressors into backing off or unsettle them so that their technique suffers, then there’s very little else it can do. It works against the average schoolyard bullies, but that’s about it.
There’s variations within all of these, but nothing else we’d categorize as unique. It’s worth looking into more though if you’re interested. People can react in a variety of ways, but whether or not those ways are going to be helpful to their specific circumstance is questionable.
I hope that helps!