Why Do We Yawn? (It's Not Oxygen)

You yawn when you're tired, bored... or just reading this. But it isn't about oxygen. Scientists tested that in the 1980s, and the real answer is stranger: your yawn may be a cooling system for your brain, and catching one might be how a group stays alert together. Chapters 0:00 You're sitting in a quiet room 0:39 The oxygen myth 0:56 Provine's gas experiment 1:30 Yawning before you're born 1:51 Every animal yawns 2:04 A radiator for your brain 2:46 The rat test 3:00 Cooling people down 3:20 Vienna vs Arizona 3:48 Bigger brains, longer yawns 4:20 Why is it contagious? 4:57 Hearing and reading yawns 5:16 Who you catch it from 5:35 The empathy idea cracks 6:10 Staying alert together 6:44 Deeper than you think 7:16 The best answer so far 7:40 Why you yawn in meetings Sources Provine, Tate & Geldmacher (1987). Behavioral and Neural Biology. CO2 and oxygen don't change yawning. https://doi.org/10.1016/S0163-1047(87... Provine (2005). Yawning. American Scientist. https://www.americanscientist.org/art... Gallup & Gallup (2007). Yawning as a brain cooling mechanism. Evolutionary Psychology. https://doi.org/10.1177/1474704907005... Shoup-Knox et al. (2010). Yawning and brain temperature in rats. Frontiers in Evolutionary Neuroscience. https://doi.org/10.3389/fnevo.2010.00108 Raichle & Gusnard (2002). The brain's energy budget. PNAS. https://doi.org/10.1073/pnas.172399499 Massen et al. (2014). Seasonal yawning in Vienna. Physiology & Behavior. https://www.sciencedaily.com/releases... Gallup & Eldakar (2011). Seasonal yawning in Arizona. Frontiers in Evolutionary Neuroscience. https://doi.org/10.3389/fnevo.2011.00003 Gallup et al. (2016). Yawn duration and brain size. Biology Letters. https://doi.org/10.1098/rsbl.2016.0545 Massen et al. (2021). Yawning in 101 species. Communications Biology. https://doi.org/10.1038/s42003-021-02... Massen, Church & Gallup (2015). Hearing yawns. Frontiers in Psychology. https://doi.org/10.3389/fpsyg.2015.01735 Campbell & de Waal (2011). Chimpanzees and in-group yawning. PLOS ONE. https://doi.org/10.1371/journal.pone.... Romero et al. (2013). Dogs catching human yawns. PLOS ONE. https://doi.org/10.1371/journal.pone.... Norscia & Palagi (2011). Yawn contagion and social closeness. PLOS ONE. https://doi.org/10.1371/journal.pone.... Bartholomew & Cirulli (2014). Empathy and contagious yawning (Duke). PLOS ONE. https://doi.org/10.1371/journal.pone.... Gallup & Meyers (2021). Yawning and spotting snakes. Animal Cognition. https://doi.org/10.1007/s10071-020-01... Walusinski et al. (2010). Arm movements during yawns after stroke. International Journal of Stroke. https://doi.org/10.1111/j.1747-4949.2... Helt et al. (2010). When children start catching yawns. Child Development. https://pubmed.ncbi.nlm.nih.gov/20840... The science isn't settled, and this video reflects the best research we could find as of 2026. Spotted a mistake? Tell us in the comments. #science #psychology #brain