Chimpanzees (Pan troglodytes) learn to act with other individuals in a cooperative task

Abstract

We presented two chimpanzees with a task in which they were required to pull each end of a rope simultaneously to drag blocks supporting food into reach. The chimpanzees did not succeed in initial tests. They did not immediately understand the necessity for cooperation, and they did not adjust their behavior to work with the partner. However, the frequency of success gradually increased as the number of sessions increased and the task was varied. They began to look at the partner frequently, wait if the partner was not holding the rope, and pull the rope in synchrony with the partner. However, they did not use interactive behaviors or eye contact to synchronize their behavior. One chimpanzee was then paired with a human partner in the same situation. After initial failures, the chimpanzee began to solicit the human partner for cooperation: looking up at his face, vocalizing, and taking the partner's hand. When this chimpanzee was again paired with the chimpanzee partner, no soliciting behavior was observed. Thus, the chimpanzees could learn to coordinate their behavior through trial and error. Communicative behavior emerged during the task, but the communication differed according to the identity of the partner.

Cooperation in wild Barbary macaques: factors affecting free partner choice

“…To our knowledge, this is the first evidence of coordinated pulling in wild macaques. Because the string was loose (Hirata and Fuwa 2007), the two ends needed to be manipulated exactly at the same time and along 75cm to bring the tray within arm's reach.…”

“…1). We used the 'loose string paradigm' of Hirata and Fuwa (2007). For this, a long rope went freely along the two boxes and tray, as well as through two pulleys placed on both extremities of the tray.…”

“…Following the 'loose string paradigm' of Hirata and Fuwa (2007), if only one monkey pulled one end of the rope, the rope moved freely through the pulleys and the tray did not move.…”

“…Different versions of this experiment have demonstrated success in simultaneous pulling in a variety of primate species (e.g. Mendres and de Waal 2000;Chalmeau et al 1997;Cronin et al 2005;Hirata and Fuwa 2007;Hare et al 2007), but also, more recently, in non-primate species such as rooks (Corvus frugilegus; Seed et al 2008;Scheid and Noë 2010), African grey parrots (Psittacus erithacus; Péron et al 2011), hyenas (Crocuta crocuta; Drea and Carter 2009), and Asian elephants (Elephas maximus; Plotnik et al 2011). Furthermore, in experiments where the arrival of the partner at the pulling apparatus was artificially delayed, some species (e.g.…”

“…partners were not artificially paired up). To solve the task, two monkeys had to manipulate simultaneously the two ends of the same rope of the apparatus in order to bring within arm's reach a tray containing a food reward for each partner (Hirata and Fuwa 2007). The Barbary macaque is a relatively tolerant species (Thierry et al 2004), yet also sharing some social features with more despotic macaque species such as low frequency of counter-aggression (Balasubramaniam et al 2012) and a steep dominance hierarchy (Kaburu et al 2012).…”