page_title: Cooperative pulling paradigm
section_title: Grey parrots
hierarchical_section_title: Cooperative pulling paradigm / Findings / Birds / Grey parrots
caption_attribution_description: Psittacus erithacus Galego: Loro gris do Congo. Foto tomada na Illa de Arousa, Galiza
context_page_description: The cooperative pulling paradigm is an experimental design in which two or more animals pull rewards toward themselves via an apparatus that they cannot successfully operate alone. Researchers use cooperative pulling experiments to try to understand how cooperation works and how and when it may have evolved.
  The type of apparatus used in cooperative pulling experiments can vary. Researcher Meredith Crawford, who invented the experimental paradigm in 1937, used a mechanism consisting of two ropes attached to a rolling platform that was too heavy to be pulled by a single chimpanzee. The standard apparatus is one in which a single string or rope is threaded through loops on a movable platform. If only one participant pulls the string, it comes loose and the platform can no longer be retrieved. Only by pulling together in coordination can the participants be successful; success by chance is highly unlikely. Some researchers have designed apparatus that involve handles instead of ropes.
  Although many animals retrieve rewards in their cooperative pulling tasks, the conclusions regarding cooperation are mixed and complex.
context_section_description: Researchers Péron, Rat-Fischer, Lalot, Nagle and Bovet had captive grey parrots (Psittacus erithacus) try to cooperate in a loose-string experimental set-up. The grey parrots were able to act simultaneously but, like the rooks, largely failed to wait for a partner in the delay task. They did not make any attempts to recruit a helping partner. The parrots did take the presence of a partner into account, since they all pulled more when a partner was present, but this could be explained by instrumental learning rather than a real understanding of the task. The researchers also gave the parrots a choice between two apparatus, one from the solo task and one from the loose-string task, now stacked with double the food per bird. Two of the three parrots chose the solo apparatus when alone, and two of the three parrots preferred the joint-task apparatus when tested with a partner. When paired up, social preferences and tolerance affected the likelihood a pair cooperated.
caption: Grey parrot
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