No one knows why we yawn. There are many theories to why we do, such as signaling tiredness, getting oxygen to the brain, reducing CO2 levels, or clearing out stale air from the lungs. These are all false. However, we all know how infectious yawns can be. No matter how much we resist, if we see someone yawn, we do the same. According to sciencebase.com, if we see someone yawning, nine out of ten times we yawn within a few seconds. Why we yawn remains a mystery.
However, researchers have found that people with autism spectrum disorder don't have the tendency to yawn when seeing others do it. Crazy, right? The Center for Brain and Cognitive Development at Birkbeck, University of London have shown that children with some degree of autism are not susceptible to contagious yawning. Atsushi Senju and colleagues set up a study where 24 children with autism spectrum and 25 non-ASD children were shown videos of people yawning or making some kind of mouth movement. The results showed that both groups yawned the same number of times when they watched the video of general mouth movements, but the non-ASD children yawned more when watching the video of people yawning.
This study is important because it displays that a neuropsychological or psychiatric condition can selectively impair contagious yawning. Autism is a developmental disability that severely affects social interaction and communication including empathy. Yawning is thought to share similar cognitive and neural mechanisms as empathy.This study confirms the 'empathy theory' in that individuals with autism, who show abnormal developments in empathy, also show selective impairment in contagious yawning.
Even though this doesn't help us to understand why we yawn, the empathy scenario provides us with and understanding regarding group behavior. So, why do we yawn and is it beneficial? Research continues to strive for an answer.