Most of us yawn during the day. The exact reason is not known, but boredom or a lack of sleep, are likely causes. Some studies have found that a yawn causes a sudden intake of oxygen, increases heart rate, and ventilates the lungs resulting in increased alertness. While the data on why we yawn is not clear it is clear that yawning is contagious. When one person yawns others around him or her are more likely to yawn. But there is one exception. Children with autism do not yawn contagiously. This makes sense to me and other clinicians who work daily with children with autism. Usually, imitation is not common in children with autism, especially those who are low functioning. The fact that children with autism do not yawn when others yawn tells me that yawning contagiously is a learned response.