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.

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