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Why yawns are contagious—in all kinds of animals - Last Episode Evolutionary biologist Andrew Gallup explains why we yawn after others Continuation from last episode, Q: Do all animals yawn the same way? A:  We’ve done a number of large-scale comparative studies, where we’ve recorded the yawn durations from over 100 mammalian and avian species. We find that even when controlling for body size, there are very strong positive relationships between how long an animal yawns and how large and complex their brain is. Q: One of the most curious things about yawning is that it can be contagious. Do all animals yawn contagiously? A: We’ve been talking about spontaneous yawns up to this point—those are internally, physiologically driven. Contagious yawns are elicited by seeing or hearing yawns in others, and [they] have only been documented in highly social species, humans included. There’s a wide variability in that response among individuals. Some individuals are very susceptible t

Why yawns are contagious—in all kinds of animals Evolutionary biologist Andrew Gallup explains why we yawn after others The mere sight of another person yawning causes many of us to open our mouths wide in mimicry. And we’re not alone—other social animals, such aschimpanzees and lions, can also catch so-called contagious yawns. It’s likely that all vertebrates yawn spontaneously to regulate inner body processes. Yawning probably arose with the evolution of jawed fishes 400 million or so years ago, says Andrew Gallup, an evolutionary biologist at State University of New York Polytechnic Institute who has spent years trying to figure out why we yawn. In a paper published this month in  Animal Behavior , he reports  some evidence  for how contagious yawns might have evolved to keep us safe.  Science  chatted with Gallup about why yawning is ubiquitous—and useful. This interview has been edited for clarity and length Q: First, let’s address a long-standing myth: Does yawning in