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This study examines the behavioural consequences of the silent bared teeth display (SBT) and the relaxed open mouth display (ROM) in the chimpanzee, and discusses functional similarities with smiling and laughing (respectively) in humans. Rates of affinitive behaviour increase (in relation to baseline levels) following SBT, suggesting that SBT is a signal of affinity. ROM is observed primarily during play, and dyadic play bouts are significantly longer when ROM is bidirectional, indicating that it may be a signal of play. Rates of affinitive behaviour also increased after ROM, suggesting that both displays may have a similar ultimate (evolutionary) function - social bonding; this could explain convergence of the two displays in humans.

Original publication

DOI

10.1111/j.1439-0310.2004.01045.x

Type

Journal article

Journal

Ethology

Publication Date

01/02/2005

Volume

111

Pages

129 - 142