system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why does our brain sometimes not initiate the fight or flee but make us unable to move when we experience intense fear?
gpt
Thing is people wrongfully call it fight or flight but the real thing is freeze-flight-fight, in that order.

Freeze is the first natural response. It not only is the most convenient way of dealing with most threats, but it also gives you time to think about what you want to do next. 

Then, if necessary, we go into flight mode. This is because even if you can win a fight, you will probably still get hurt, which can mean certain death in the long run (unable to hunt, run away etc)

Lastly, we fight.

You can read more about it in Joe Navarro's book What Every Body Is Saying.