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Recently, yawn duration was shown to be a robust predictor of brain size and complexity across a diverse sample of mammalian species. In particular, mammals with larger brains and more cortical neurons have longer yawns on average. Here, we investigated whether this relationship between yawn duration and brain size, which was previously at the taxonomic rank of class, is also present within a more restricted scale: a family of mammals. Using previously published data on brain weight and endocranial volumes among various field species within the family Felidae, we ran correlations with yawn durations obtained from openly accessible videos on the Internet. Consistent with previous findings, we show a strong linear relationship between yawn duration and both brain weight and brain volumes among wild cats. However, yawn duration was not significantly correlated with species body weight. Although limited to a small sample, these results provide convergent evidence for an important and general neurophysiologic function to yawning and highlight the utility of measuring yawn duration in comparative research.

The document explores emotional contagion in animals, highlighting its role in promoting synchronization, affiliation, and prosocial behavior within animal groups. Researchers from various fields have shown interest in understanding the mechanisms of emotional contagion, which is considered a substructure for advanced forms of empathy. The Special Issue collates research on psychological and behavioral correlates, proximate mechanisms, adaptive significance, and challenges in studying emotional contagion in animals, showcasing diverse approaches and contributions from authors worldwide. The six articles published cover topics such as empathy in domesticated dogs and cats, physiological responses of goats, interspecific contagious yawning, emotional contagion in piglets, and empathy-like behaviors in dogs, contributing to a better understanding of emotional contagion and its applications in animal welfare and human mental health. [Extracted from the article]

Comparative research suggests that yawning is a thermoregulatory behavior in homeotherms. Our previous experiments revealed that yawning increased in budgerigars (Melopsittacus undulatus) as ambient temperature was raised toward body temperature (22[right arrow]34[degrees]C). In this study, we identify the range of temperatures that triggers yawning to rule out the possible effect of changing temperature in any range. To corroborate its thermoregulatory function, we also related the incidence of yawning to other avian thermoregulatory behaviors in budgerigars (e.g., panting, wing venting). In a repeated measures design, 16 budgerigars were exposed to 4 separate 10-min periods of changing temperatures: (a) low-increasing (23[right arrow]27[degrees]C), (b) high-increasing (27[right arrow]33[degrees]C), (c) high-decreasing (34[right arrow]28[degrees]C), and (d) low-decreasing (28[right arrow]24[degrees]C). Birds yawned significantly more during the high-increasing temperature range, and yawning was positively correlated with ambient temperature across trials. Yawning was also positively correlated with other thermoregulatory behaviors. This research clarifies the previously demonstrated relationship between yawning rate and temperature by providing evidence that the physiological trigger for yawning is related to increasing body temperatures rather than the detection of changing external temperatures. Keywords: yawning, ambient temperature, brain cooling, thermoregulation, Melopsittacus undulatus DOI: 10.1037/a0018006