• Chimpanzees modify intentional gestures to coordinate a search for hidden food

      Roberts, Anna I.; Vick, Sarah-Jane; Roberts, Sam G. B.; Menzel, Charles R.; University of Chester; University of Stirling; Georgia State University (Nature Publishing Group, 2014-01-16)
      Humans routinely communicate to coordinate their activities, persisting and elaborating signals to pursue goals that cannot be accomplished individually. Communicative persistence is associated with complex cognitive skills such as intentionality, because interactants modify their communication in response to another’s understanding of their meaning. Here we show that two language-trained chimpanzees effectively use intentional gestures to coordinate with an experimentally naive human to retrieve hidden food, providing some of the most compelling evidence to date for the role of communicative flexibility in successful coordination in nonhumans. Both chimpanzees (named Panzee and Sherman) increase the rate of non-indicative gestures when the experimenter approaches the location of the hidden food. Panzee also elaborates her gestures in relation to the experimenter’s pointing, which enables her to find food more effectively than Sherman. Communicative persistence facilitates effective communication during behavioural coordination and is likely to have been important in shaping language evolution.
    • Justify Your Alpha

      Lakens, Daniel; Adolfi, Federico G.; Albers, Casper J.; Anvari, Farid; Apps, Matthew A. J.; Argamon, Shlomo E.; Baguley, Thom; Becker, Raymond B.; Benning, Stephen D.; Bradford, Daniel E.; et al. (Nature Publishing Group, 2018-02-26)
      In response to recommendations to redefine statistical significance to p≤ .005, we propose that researchers should transparently report and justify all choices they make when designing a study, including the alpha level
    • Wild chimpanzees modify modality of gestures according to the strength of social bonds and personal network size

      Roberts, Anna I.; Roberts, Sam G. B.; University of Chester (Nature Publishing Group, 2016-09-21)
      Primates form strong and enduring social bonds with others and these bonds have important fitness consequences. However, how different types of communication are associated with different types of social bonds is poorly understood. Wild chimpanzees have a large repertoire of gestures, from visual gestures to tactile and auditory gestures. We used social network analysis to examine the association between proximity bonds (time spent in close proximity) and rates of gestural communication in pairs of chimpanzees when the intended recipient was within 10 m of the signaller. Pairs of chimpanzees with strong proximity bonds had higher rates of visual gestures, but lower rates of auditory long-range and tactile gestures. However, individual chimpanzees that had a larger number of proximity bonds had higher rates of auditory and tactile gestures and lower rates of visual gestures. These results suggest that visual gestures may be an efficient way to communicate with a small number of regular interaction partners, but that tactile and auditory gestures may be more effective at communicating with larger numbers of weaker bonds. Increasing flexibility of communication may have played an important role in managing differentiated social relationships in groups of increasing size and complexity in both primate and human evolution.