You're lost in the wilderness, and have been looking all day for food. You don't find much, and are still hungry. Then, you find a bush like you've never seen, with tons of berries... but you don't know if they're poisonous or not. Do you eat them, or go hungry? You might be saved soon... or you might not, who knows.
Probably not. If it's really the wilderness there's probably going to be other stuff around which is much safer, although I'd imagine far less pleasant, to eat and I'd go for that. Not like you can really sustain yourself on berries anyway! But I just know that being lost and sick would be far worse than being lost and not having the usual pleasant meals.
I probably wouldn't... Maybe I would feed some animals (maybe) and see if they die or not. If they don't I might resort to eating these berries, but I'd rather try and look for other food that I'm certain is not poisonous.
I'd eat one of the berries and see if I still don't feel well after a few hours. If I do, I try to look for other berries or start hunting for animals.
I'd wait off until it has been a bit longer. You can last quite a while without food, so I'd see if I find anything else that I know is safe, or if I get rescued in that time, but I'd pick them and keep them as a last resort.
I know a lot about wild berries, so I won't have any trouble with deciding to wether or not to eat a bunch of berries in a bush.
I won't hesitate to hunt a wild animal (preferably rabbit) if all I find are poisonous berries.