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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 expressions, as a function of modality of expression and type of play. The modality × play type interaction was examined by comparing playful expression rates for each modality across social and solitary play contexts (paired t-tests) and by comparing the playful expression rates for each modality within each play context (One-Way ANOVA with simple contrasts). *p < 0.05, **p < 0.01, ***p < 0.001.
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Figure 1: Mean rate (intervals per minute of play, with SE) of chimpanzee infants' playful expressions, as a function of modality of expression and type of play. The modality × play type interaction was examined by comparing playful expression rates for each modality across social and solitary play contexts (paired t-tests) and by comparing the playful expression rates for each modality within each play context (One-Way ANOVA with simple contrasts). *p < 0.05, **p < 0.01, ***p < 0.001.

Mentions: Infant play time consisted of a higher proportion of solitary play than social play (mean solitary = 66% ± SD 6%; mean social = 34% ± SD 6%; F = 48.52, df = 1, 6, p < 0.001, η2P = 0.89). Playful expression rate was examined by play context and by modality and there was a significant effect of play context (F = 81.12, df = 1, 6, p < 0.001, η2P = 0.93), a significant effect of modality (F = 14.28, df = 1.14, 6.82, p < 0.01, η2P = 0.70), and a significant interaction between modality and play context (F = 28.62, df = 1.04, 6.25, p < 0.001, η2P = 0.83). Post-hoc comparisons (see Figure 1) showed that play face rate and multimodal rate were significantly higher during social play than during solitary play, while body rate did not differ by play context. During social play, play face rate was significantly higher than body rate and multimodal rate. During solitary play, play face rate was significantly lower than body rate and significantly higher than multimodal rate. All six expression rates shown in Figure 1 were significantly higher than 0 (i.e., 95% confidence interval surrounding the intercept did not include 0; ts > 2.95, ps < 0.03).


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 expressions, as a function of modality of expression and type of play. The modality × play type interaction was examined by comparing playful expression rates for each modality across social and solitary play contexts (paired t-tests) and by comparing the playful expression rates for each modality within each play context (One-Way ANOVA with simple contrasts). *p < 0.05, **p < 0.01, ***p < 0.001.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Figure 1: Mean rate (intervals per minute of play, with SE) of chimpanzee infants' playful expressions, as a function of modality of expression and type of play. The modality × play type interaction was examined by comparing playful expression rates for each modality across social and solitary play contexts (paired t-tests) and by comparing the playful expression rates for each modality within each play context (One-Way ANOVA with simple contrasts). *p < 0.05, **p < 0.01, ***p < 0.001.
Mentions: Infant play time consisted of a higher proportion of solitary play than social play (mean solitary = 66% ± SD 6%; mean social = 34% ± SD 6%; F = 48.52, df = 1, 6, p < 0.001, η2P = 0.89). Playful expression rate was examined by play context and by modality and there was a significant effect of play context (F = 81.12, df = 1, 6, p < 0.001, η2P = 0.93), a significant effect of modality (F = 14.28, df = 1.14, 6.82, p < 0.01, η2P = 0.70), and a significant interaction between modality and play context (F = 28.62, df = 1.04, 6.25, p < 0.001, η2P = 0.83). Post-hoc comparisons (see Figure 1) showed that play face rate and multimodal rate were significantly higher during social play than during solitary play, while body rate did not differ by play context. During social play, play face rate was significantly higher than body rate and multimodal rate. During solitary play, play face rate was significantly lower than body rate and significantly higher than multimodal rate. All six expression rates shown in Figure 1 were significantly higher than 0 (i.e., 95% confidence interval surrounding the intercept did not include 0; ts > 2.95, ps < 0.03).

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