"The experimenter explained that the box of to ys the children could pick from depended on the total number points they earned by guessing doors with either gre

"The experimenter explained that the box of to ys the children could pick from depended on the total number points they earned by guessing doors with either green vs red arrows behind them." Sounds the same to me as what OP suggested. Even as a child (as early as I remember) I hated praise and rewards when I didn't feel I had deserved it by my own efforts. Guessing random events is not among things I consider conscious effort. Furthermore, children background could have impact too: the one from poorer family would be happier to receive a small gift versus the one from rich family that already has a room full of all the toys he could want.