It's long been assumed that yawning delivers a fresh supply of oxygen to the brain to help us wake up, but studies have been unable to show an increase in blood oxygen levels after yawning. 
 
 Now Austrian researchers have found that yawning actually works to manage brain temperature to improve alertness and mental efficiency. 
 
 We tend to yawn when we are tired, stressed or under-stimulated, which are all factors that can alter the temperature of the brain, and the University of Vienna researchers tested whether air temperature could influence how much we yawn. 
 
 The researchers showed pictures of people yawning to pedestrians in Vienna in order to spark contagious yawning. They conducted the test in both summer months and winter months to see how air temperature affected their yawning frequency. 
 
 They compared the results to a similar US study conducted in Arizona, where the climate is arid, and found that people in Vienna yawn more in summer than winter, while people in Arizona yawn more in winter than summer. 
 
 The researchers concluded that contagious yawning is most frequent when the temperature is around 20°C. 
 
 Yawning frequency reduced when temperatures were around 37°C in Arizona's summer and also in the freezing depths of the Vienna winter. 
 
 Lead author Dr Jorg Massen said yawning appears to be unhelpful when the air temperature is as hot as the body, or when it is freezing, as the cold air is unnecessary or could even be harmful. 
 
 Source: Science Daily Author: Kimberly Gillan; Approving editor: Rory Kinsella ||||| Common belief is that yawning helps to increase the oxygen supply. However, previous research has failed to show an association between yawning and blood oxygen levels. New research by a team of researchers led by Psychologist Andrew Gallup of SUNY College at Oneonta, USA now reveals that yawning cools the brain. 
 
 Sleep cycles, cortical arousal and stress are all associated with fluctuations in brain temperature, Yawning subsequently functions to keep the brain temperature balanced and in optimal homeostasis. According to this theory, yawning should also be easily manipulated by ambient temperature variation, since exchange with cool ambient air temperature may facilitate lowering brain temperature. Specifically, the researchers hypothesized that yawning should only occur within an optimal range of temperatures, i.e., a thermal window. 
 
 To test this, Jorg Massen and Kim Dusch of the University of Vienna measured contagious yawning frequencies of pedestrians outdoors in Vienna, Austria, during both the winter and summer months, and then compared these results to an identical study conducted earlier in arid climate of Arizona, USA. Pedestrians were asked to view a series of images of people yawning, and then they self-reported on their own yawning behavior. 
 
 Results showed that in Vienna people yawned more in summer than in winter, whereas in Arizona people yawned more in winter than in summer. It turned out that it was not the seasons themselves, nor the amount of daylight hours experienced, but that contagious yawning was constrained to an optimal thermal zone or range of ambient temperatures around 20o C. In contrast, contagious yawning diminished when temperatures were relatively high at around 37o C in the summer of Arizona or low and around freezing in the winter of Vienna. Lead author Jorg Massen explains that where yawning functions to cool the brain, yawning is not functional when ambient temperatures are as hot as the body, and may not be necessary or may even have harmful consequences when it is freezing outside. 
 
 While most research on contagious yawning emphasizes the influence of interpersonal and emotional-cognitive variables on its expression, this report adds to accumulating research suggesting that the underlying mechanism for yawning, both spontaneous and contagious forms, is involved in regulating brain temperature. In turn, the cooling of the brain functions to improve arousal and mental efficiency. The authors of this study suggest that the spreading of this behavior via contagious yawning could therefore function to enhance overall group vigilance. ||||| The thermoregulatory theory of yawning posits that yawns function to cool the brain in part due to counter-current heat exchange with the deep inhalation of ambient air. Consequently, yawning should be constrained to an optimal thermal zone or range of temperature, i.e., a thermal window, in which we should expect a lower frequency at extreme temperatures. Previous research shows that yawn frequency diminishes as ambient temperatures rise and approach body temperature, but a lower bound to the thermal window has not been demonstrated. To test this, a total of 120 pedestrians were sampled for susceptibly to self-reported yawn contagion during distinct temperature ranges and seasons (winter: 1.4 °C, n = 60; summer: 19.4 °C, n = 60). As predicted, the proportion of pedestrians reporting yawning was significantly lower during winter than in summer (18.3% vs. 41.7%), with temperature being the only significant predictor of these differences across seasons. The underlying mechanism for yawning in humans, both spontaneous and contagious, appears to be involved in brain thermoregulation. ||||| Why Did You Just Yawn? Perhaps Your Brain's Too Hot 
 
 Chances are you read this sentence about yawning and you yawned. Right? Well, a new study suggests that you may not really be yawning because it's contagious, or you're bored or tired. 
 
 You're actually yawning because your brain is too hot. 
 
 A group of researchers at the University of Vienna tested subjects in Austria and Arizona and tracked their activity, finding that that the only significant predicator of yawning was temperature: subjects were much more likely to yawn at higher temperatures. Other factors like sex, season, age, humidity, time spent outside, and hours of sleep the night before did not have a significant effect on the likelihood of a subject's yawning. 
 
 Ultimately, it appears that yawning is related to regulating brain temperature and creating a state where arousal in a yawner can be achieved. The idea is that if it's hot, but still cool enough so that a large intake of air will bring your body temperature down, you're in perfect storm territory for yawns. 
 
 The study builds on research that shows that in both rats and humans, yawns are preceded by intermittent rises in brain temperatures, and that brain temperature decreases immediately afterward.
– If you're yawning a lot, check the temperature: Researchers say we may yawn when it's warm out because that cools down the brain. In the study, which agrees with earlier research, experts at the University of Vienna showed pictures of yawns to pedestrians in Austria and Arizona, ScienceDaily reports; they aimed to induce contagious yawning, ninemsn explains. After the study was conducted in both summer and winter, researchers found that such yawns occurred most often at temperatures around 68 degrees Fahrenheit. The scientists argue that there's a "thermal window for yawning," and it opens when we're warm but the air is cool enough for a yawn to lower our temperatures, Time reports. Previous research has indicated that we yawn after our body temperatures rise. The study found that people's age, sex, and previous night's sleep, on the other hand, didn't have much of an effect on our yawning patterns. All this talk of temperature still fits the idea that we yawn when sleepy, ninemsn notes. Tiredness, stress, and a lack of stimulation can have an effect on our brain temperatures.