There are other prevalent theories about why we yawn. One that's incorrect is the idea that we yawn in order to take in more oxygen. You're gulping in a lot of air, so it isn't necessarily surprising that most people think yawning has some sort of respiratory function, admits Dr. Gallup. However, that hypothesis has been thoroughly tested and debunked, he says. In studies, participants who receive less oxygen don't yawn more frequently than those in normal conditions. And exercising, which can double our breathing rate, doesn't seem to make us yawn more often, either.Another hypothesis — that actually has some evidence to support it — is that there's some sort of social function to our yawning. Although Dr. Gallup says there's no consensus about what that function might be, we do know that yawns can be contagious. You're more likely to yawn if you see, hear, or even just think about someone yawning, Dr. Gallup explains. And while many animals yawn spontaneously (for physiological reasons), far fewer yawn contagiously. Those that do tend to be particularly social species, such as humans, chimps , and even parakeets Some research has suggested that this social connection might be mirrored in our levels of empathy. The general idea is that those who are more empathetic are more susceptible to contagious yawning. One particularly bold study found that those who score higher on measures of psychopathology are actually less vulnerable to contagious yawning. And while some research does support the empathy connection, Dr. Gallup says there are other studies in this line of thinking that have been inconclusive or contradictory.Even if yawning isn't a window into our personalities, it's clear that it's a useful behavior. The fact that we share it with so many other species (especially mammals like ourselves) suggests that it has been evolutionarily beneficial. We're just not quite sure how — yet.