Human laughter, social play, and play vocalizations of non-human primates: an evolutionary approach

摘要

It has been hypothesized that the evolutionary origin of human laughter lies in the facial play signals of non-human primates. Recent studies dealing with human laughter have stressed the importance of the acoustic component of this nonverbal behaviour. In this study, we analysed the occurrence and some acoustic parameters, such as interval durations and fundamental frequency, of Barbary macaque and chimpanzee play vocalizations and human laughter during tickling. Play vocalizations occurred most often during play with close bodily contact, i.e. wrestling and tickling. In both Barbary macaques and chimpanzees, they were serially organized and had a high intra-bout variability in their acoustic parameters. These are characteristic features of human laughter which are crucial for deciding whether a given utterance will be classified as laughter in humans. Besides intra-bout variability, there was substantial intraindividual variability which was as high or higher than the interindividual variabilityin all three species. Interval durations of Barbary macaque and chimpanzee play vocalizations and human laughter during tickling lay in a similar range. These results provide further evidence for the hypothesis that human laughter evolved from a play signal of non-human primates and raise questions about the importance of and the relationship between facial and vocal play signals in the evolution of human laughter.