Give the dog a bone—or else he might not be willing to sit and shake for one again. Researchers have observed that when a dog sees another dog getting a treat for a similar task but does not receive one itself, he is less likely to cooperate in the future. This suggests that animals may have a sense of inequity aversion similar to humans. But tangible rewards aren’t the only motivating forces in cooperation. A study on punishment in game theory found that “people were more likely to cooperate with one another in games when they had the option to punish cheats,” wrote ScienceBlogger Ed Yong.