狗这样表现可不只是因为他们得不到奖赏，研究者稍后单独测验了狗狗们的表现，发现此条件下那妒火中烧的狗在停下不做之前合作了更长的时间。

To show this was not just because the animals were not getting food, the researchers then tested the dogs alone and found that in this situation the envious canines cooperated longer before stopping.

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