This is quite opposite to the view of some economists and anthropologists, who postulate the differences between humans and other animals. However, recent work on prosocial tendencies in apes and monkeys supports de Waal's position. See, for example, the research of Felix Warneken, a psychologist at the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany. In 2011, de Waal and his co-workers were the first to report that chimpanzees given a free choice between helping only themselves or helping themselves plus a partner, prefer the latter. In fact, de Waal does not believe these tendencies to be restricted to humans and apes, but views empathy and sympathy as universal mammalian characteristics, a view that over the past decade has gained support from studies on rodents and other mammals, such as dogs. He and his students have also extensively worked on cooperation and fairness in animals, the latter leading to a video that went viral on inequity aversion among capuchin monkeys. The most recent work in this area was the first demonstration that given a chance to play the Ultimatum game, chimpanzees respond in the same way as children and human adults by preferring the equitable outcome.