This study investigated the ability of chimpanzees (Pan troglodytes) to understand non-transitive relationships by training them in the rules of the Rock-Paper-Scissors (RPS) game. Seven chimpanzees were trained to perform a computer-controlled discrimination task. Each task used two figures, representing two of the three elements in each trial, which were completed in the following order: Paper-Rock sessions; Rock-Scissor sessions; Scissor-Paper sessions; and finally, mixed-pair sessions. The chimpanzees received a food reward every time they chose the correct figure. They had three sessions of 48 trials each day. On average, they received 339 training sessions. Four of the seven chimpanzees completed training. Three of them then received generalization tests using different stimuli with the same circular relationship, and one of the three passed the new task in 23 sessions. These results suggest that chimpanzees could learn about non-transitive relationships, and they are able to generalize this circular concept to new stimuli.
Adenoviruses are widespread in African great apes as well as in human population. Although recent studies have described the ancient gorillas to be the origin of the species Human mastadenovirus B, more comprehensive studies are still needed to unravel the mechanisms driving the evolution of adenoviruses. We conducted the surveillance of adenovirus infection in wild western lowland gorillas in Moukalaba-doudou National Park (Gabon), in order to investigate naturally occurring adenovirus in target gorillas and tested specifically a possible zoonotic transmission with local people inhabiting the vicinity of the park. Fecal samples were collected from western lowland gorillas and humans, and analyzed by PCR. We detected adenoviral genes in samples from both gorillas and the local people living around the national park respectively: the overall prevalence rates of adenovirus were 24.1% and 35.0% in gorillas and humans, respectively. Sequencing revealed that the adenoviruses detected in the gorillas were members of Human mastadenovirus B (HAdV-B), HAdV-C, or HAdV-E, and those in the humans belonged to HAdV-C or HAdV-D. Although HAdV-C members were detected in both gorillas and humans, phylogenetic analysis revealed that the virus detected in gorillas are genetically distinct from those detected in humans. The HAdV-C constitutes a single host lineage which is compatible with the host-pathogen divergence. However, HAdV-B and HAdV-E are constituted by multiple host lineages. Moreover there is no evidence of zoonotic transmission thus far. Since the gorilla-to-human transmission of adenovirus has been shown before, the current monitoring should be continued in a broader scale for gaining more insights about the naturally occurring adenoviruses which would be helpful for the safe management of gorilla populations and human health.