‘Reaction totally necessary’: Brother scares sister when she’s alone at night, and she somehow gives a fight AND flight response

Scaring your sibling is a familial right — a sacred duty, if you will, that every one of us with big families solemnly takes on.

There’s a dedicated prankster in almost every family, and in TikToker Katlyn’s household, that role goes to her brother. He seems to be a pro, based on a recent upload to his sister’s page, in which he manages to elicit two of the four main fear responses out of her all at once.

In a video that racked up more than 3.5 million views and a whopping 803,400 likes, the supreme talent of Katlyn’s family prankster is on full display. Edging up on his sister in the middle of the night — and the middle of a creepy stairwell, no less — this evil icon takes up the perfect position to give his sister a proper heart attack.

Crouching just on the other side of the door, he’s perfectly poised to film his sister’s priceless reaction to his little stunt. And priceless it is, as Katlyn enters the hall, unsuspecting, and promptly combines her fight and flight responses into one glorious outburst.

It’s a truly delightful moment to watch, particularly as Katlyn walks away to the hysterical giggles of her mischievous kin. It also prompted some similarly hysterical responses from viewers, who are tacking a fresh fear response onto the established quartet. “Fight, flight, freeze, or flip off,” is apparently the new set of nervous system responses to fear, and we couldn’t be more here for it.

Most everyone learned about fight or flight in school, but — minus the “flip off,” — there are actually already four established responses to fear. Fight and flight still lead the pack, but over the years they’ve been joined by freeze and fawn, two other common responses to a frightening situation. It seems familial fear simply hits different, however, and adds a “secret fifth nervous system response” to the mix.