What is the title of A book about 4 kids trapped in an experiment in a building?

In elem. school [between 1992 and1993] I read this fiction/scifish book about a girl (teen)who wakes up to find she's trapped in a room/building with 3? other kids (2 boys and another girl. No one else is around but they figure out they are being watched. Any time the kids are directed by some silent hand to do something...they are rewarded in some fashion for example food. Not doing what their directed denies them any chance of sustenance. It was a weird book but I remember being engrossed in it and rooting for the protagonist who seems, if i recall well, to befriend one of the boys. The other two kids seem to be more selfish aka bad seeds, doing whatever they need to get a reward including eventually turning on the girl and her friend ( bullying them ?? ) I believe the end of the book turns out to be this female protagonist and her male friend being allowed out of their prison/experimental room after the "observers" are particularly satisfied at a show of positive human nature on the girl and boy's part. The kids seem weak and undernourished but manage to get out while it is umed the other kids didn't fare as well and remained in captivity. I was left with the sense, as a kid that these four kids were part of some sort of behavioral experiment. I would love to find this book. It nags me now even at 28 that I can't remember anything about the title. Plus i'd LOVE to read it again.