Behavioral experiment by Max-Planck-Institute for Ornithology at Loro Parque © Comparative Cognition Group
Now, I don't know how it works between an African Grey parrot and a human, but between two African Greys, "What's mine is yours. Period."
This was demonstrated in a study by the Max-Planck-Institute for Ornithology where one African Grey parrot, Bella, had been trained to give a token to a researcher in return for her favorite food. In the box next to her was Kimmi, who had not been trained, but who had watched Bella in the act of trading tokens for food.
The problem was that Kimmi had no tokens. But when Kimmi's treat window opened, Bella gave Kimmi the tokens he needed to get the treats.
You have to see this to believe it.
Though feeding one's young is natural to almost all living species, giving charitably had only thus far been seen in humans and great apes. Observing the behavior between Bella and Kimmi, one has to see it as charitable. And when Bella wanted to get her rewards, Kimmi provided them too, as you'll see below. This reciprocity "is seen as an important prerequisite for the evolution of cooperation." (via)
In the first part of the video below, we see Kimmi reciprocating Bella's generosity, but watch what happens in the second part, when two Blue-headed Macaws are given the same opportunity to help each other:
Indeed, as far as scientists have evidenced, the African Grey is the only avian representative known to help others out without expectation of something in return. Auguste von Bayern, the leader of the comparative cognition research group theorizes that perhaps it's because parrots mate for life and are inter-dependent.... But there are other bird species that mate for life that don't show these tendencies.
Perhaps, then, it is also because parrots are very smart! If you have members of the parrot family at your home, look for signs of unselfish behavior between birds, and even between you and your birds.
The research for this study was conducted at Loro Parque (Parrot Park) in Tenerife, Spain, set up in 1972 as a 'paradise for parrots.' Now, with more than 4,000 parrots among 350 species, the Park has really become a zoo, housing many other birds and animals as well. The popular park is a research paradise for many of the Max-Planck-Institute for Ornithology studies, including its most recent one on a behaviorial aspect of African Grey parrots.