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Playful expressions of one-year-old chimpanzee infants in social and solitary play contexts.

Ross KM, Bard KA, Matsuzawa T - Front Psychol (2014)

Bottom Line: No group or age differences were found in the rate of infant playful expressions.Matched expression rates were highest when playing with peers despite infant expressiveness being highest when playing with older chimpanzees.Given that playful expressions emerge early in life and continue to occur in solitary contexts through the second year of life, we suggest that the play face and certain body behaviors are emotional expressions of joy, and that such expressions develop additional social functions through interactions with peers and older social partners.

View Article: PubMed Central - PubMed

Affiliation: Department of Psychology, University of Winchester Winchester, UK ; Department of Psychology, Centre for Comparative and Evolutionary Psychology, University of Portsmouth Portsmouth, UK.

ABSTRACT
Knowledge of the context and development of playful expressions in chimpanzees is limited because research has tended to focus on social play, on older subjects, and on the communicative signaling function of expressions. Here we explore the rate of playful facial and body expressions in solitary and social play, changes from 12- to 15-months of age, and the extent to which social partners match expressions, which may illuminate a route through which context influences expression. Naturalistic observations of seven chimpanzee infants (Pan troglodytes) were conducted at Chester Zoo, UK (n = 4), and Primate Research Institute, Japan (n = 3), and at two ages, 12 months and 15 months. No group or age differences were found in the rate of infant playful expressions. However, modalities of playful expression varied with type of play: in social play, the rate of play faces was high, whereas in solitary play, the rate of body expressions was high. Among the most frequent types of play, mild contact social play had the highest rates of play faces and multi-modal expressions (often play faces with hitting). Social partners matched both infant play faces and infant body expressions, but play faces were matched at a significantly higher rate that increased with age. Matched expression rates were highest when playing with peers despite infant expressiveness being highest when playing with older chimpanzees. Given that playful expressions emerge early in life and continue to occur in solitary contexts through the second year of life, we suggest that the play face and certain body behaviors are emotional expressions of joy, and that such expressions develop additional social functions through interactions with peers and older social partners.

No MeSH data available.


Related in: MedlinePlus

Mean rate (intervals per minute of play, with SE) of chimpanzee infants' playful body expressions during social and solitary play. *p < 0.05.
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Figure 2: Mean rate (intervals per minute of play, with SE) of chimpanzee infants' playful body expressions during social and solitary play. *p < 0.05.

Mentions: Body expressions were subdivided into five types: hitting (32%), acrobatics (28%), flailing limbs (22%), bouncing (15%), and tickle requests (2%). Expression rate was examined by body type and play context. Body type had a significant effect on expression rate (F = 5.80, df = 4, 24, p < 0.01, η2p = 0.49), and there was a significant interaction between body type and play context (F = 5.01, df = 1.86, 11.17, p < 0.01, η2p = 0.46) (Figure 2). Pairwise comparisons (Bonferonni adjusted) found that the rates of hitting and acrobatics were higher than the rate of tickle requests. Comparisons of expression rates for each body type across social and solitary play found no significant differences despite some moderate effect sizes (Fs < 5.97, df = 1, 6, ps > 0.05, η2p range = 0.12–0.50). Note that although tickle request expressions were observed only during social play, four infants never displayed this expression. During social play, the rates of acrobatics, hitting, and flailing limbs were significantly higher than 0 (i.e., the 95% confidence interval of the intercept did not include 0, ts > 2.91, ps < 0.03). During solitary play, all expression rates were significantly higher than 0 (ts > 3.02, ps < 0.03), with the exception of tickle requests.


Playful expressions of one-year-old chimpanzee infants in social and solitary play contexts.

Ross KM, Bard KA, Matsuzawa T - Front Psychol (2014)

Mean rate (intervals per minute of play, with SE) of chimpanzee infants' playful body expressions during social and solitary play. *p < 0.05.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4109582&req=5

Figure 2: Mean rate (intervals per minute of play, with SE) of chimpanzee infants' playful body expressions during social and solitary play. *p < 0.05.
Mentions: Body expressions were subdivided into five types: hitting (32%), acrobatics (28%), flailing limbs (22%), bouncing (15%), and tickle requests (2%). Expression rate was examined by body type and play context. Body type had a significant effect on expression rate (F = 5.80, df = 4, 24, p < 0.01, η2p = 0.49), and there was a significant interaction between body type and play context (F = 5.01, df = 1.86, 11.17, p < 0.01, η2p = 0.46) (Figure 2). Pairwise comparisons (Bonferonni adjusted) found that the rates of hitting and acrobatics were higher than the rate of tickle requests. Comparisons of expression rates for each body type across social and solitary play found no significant differences despite some moderate effect sizes (Fs < 5.97, df = 1, 6, ps > 0.05, η2p range = 0.12–0.50). Note that although tickle request expressions were observed only during social play, four infants never displayed this expression. During social play, the rates of acrobatics, hitting, and flailing limbs were significantly higher than 0 (i.e., the 95% confidence interval of the intercept did not include 0, ts > 2.91, ps < 0.03). During solitary play, all expression rates were significantly higher than 0 (ts > 3.02, ps < 0.03), with the exception of tickle requests.

Bottom Line: No group or age differences were found in the rate of infant playful expressions.Matched expression rates were highest when playing with peers despite infant expressiveness being highest when playing with older chimpanzees.Given that playful expressions emerge early in life and continue to occur in solitary contexts through the second year of life, we suggest that the play face and certain body behaviors are emotional expressions of joy, and that such expressions develop additional social functions through interactions with peers and older social partners.

View Article: PubMed Central - PubMed

Affiliation: Department of Psychology, University of Winchester Winchester, UK ; Department of Psychology, Centre for Comparative and Evolutionary Psychology, University of Portsmouth Portsmouth, UK.

ABSTRACT
Knowledge of the context and development of playful expressions in chimpanzees is limited because research has tended to focus on social play, on older subjects, and on the communicative signaling function of expressions. Here we explore the rate of playful facial and body expressions in solitary and social play, changes from 12- to 15-months of age, and the extent to which social partners match expressions, which may illuminate a route through which context influences expression. Naturalistic observations of seven chimpanzee infants (Pan troglodytes) were conducted at Chester Zoo, UK (n = 4), and Primate Research Institute, Japan (n = 3), and at two ages, 12 months and 15 months. No group or age differences were found in the rate of infant playful expressions. However, modalities of playful expression varied with type of play: in social play, the rate of play faces was high, whereas in solitary play, the rate of body expressions was high. Among the most frequent types of play, mild contact social play had the highest rates of play faces and multi-modal expressions (often play faces with hitting). Social partners matched both infant play faces and infant body expressions, but play faces were matched at a significantly higher rate that increased with age. Matched expression rates were highest when playing with peers despite infant expressiveness being highest when playing with older chimpanzees. Given that playful expressions emerge early in life and continue to occur in solitary contexts through the second year of life, we suggest that the play face and certain body behaviors are emotional expressions of joy, and that such expressions develop additional social functions through interactions with peers and older social partners.

No MeSH data available.


Related in: MedlinePlus