Laughter, play faces and mimicry in animals: evolution and social functions

Area of Science:

• Evolutionary biology
• Comparative psychology
• Neuroscience

Background:

• Human laughter and laugh faces exhibit morphological and functional parallels with animal playful expressions.
• Understanding these positive expressions in animals is crucial for elucidating the primordial uses and effects of human laughter.

Purpose of the Study:

• To examine the evolution and function of playful expressions in primates and other animals.
• To investigate the homologous and analogous systems underlying these positive emotional expressions.

Main Methods:

• Phylogenetic research on hominids to establish shared ancestry of emotional expressions.
• Analysis of muscle activations in the open-mouth play faces of six carnivore taxa.
• Comparative study of playful expressions across primates and other animal groups.

Main Results:

• Carnivore open-mouth play faces were identified as homologues of primate open-mouth play faces based on muscle activation patterns.
• Animal play expressions play a significant role in developing social cognitive skills, potentially explaining their polyphyletic distribution.
• These expressions communicate positive emotions and enhance affiliation and bonding through motor resonance, similar to human laughter.

Conclusions:

• Playful expressions in animals, including laughter, have deep evolutionary origins and serve crucial social functions.
• The findings support a shared biological basis for positive emotional communication and social bonding across diverse species.
• This research contributes to understanding the biological underpinnings of laughter and its role in social interactions.