It’s mostly scripted, this. Or at lease rehearsed and they say “yes, that’s good leave that in”, “no, that’s no good leave that out” “try that again, only this time really act like you’re scared/shocked/laughing”...
None or little of the reactions are natural. Much of it is like watching the world’s worst actors attempting to act.
A workmate’s husband works in television and he’s said in the past that next to nothing on television isn’t scripted and/or rehearsed anymore. Programmes like Love Island and Big Brother are given plots to ad lib along to the story line given to them.
Even comedy panel game shows are rehearsed and they add in scripted jokes and pretend they’re off the cuff. You don’t notice the first time you watch it, but if you ever watch a repeat of a comedy panel game show on Dave or wherever, you can tell. And you can tell with Gogglebox on first viewing, that it’s a second or third viewing for them of the thing they’re pretending to react to a first time.