WASHINGTON – Acting selflessly to help others in need was long thought to be a trait confined to mammals, in particular humans and great apes. But a new study has found that African gray parrots volunteer assistance to both their good friends and mere acquaintances -- even when there is no expectation of personal gain. The paper, published Thursday in the journal Current Biology, advances our knowledge of the evolution of cooperation and social intelligence, co-author Auguste von Bayern of the Max Planck Institute for Ornithology in Starnberg, Germany, said. Both parrots and birds such as crows and ravens are renowned for their extraordinary problem-solving skills, and are sometimes called "feathered apes." Alex, the famous Harvard-based African gray parrot that died in 2007, developed a vocabulary of over 100 words, could identify colors and quantify objects up to the number six, among many other accomplishments.