Anyone with a little knowledge of biology and a sense of mischief will know that intentionally yawning in a public place can set off a chain reaction. But a newly-published study explores why children with autism are less vulnerable to the “sympathetic yawn.”

A common theory is that the reason we yawn when we see somebody else yawn (even when we aren’t tired) is that we subconsciously want to show empathy and strengthen social bonds. That’s created some speculation that autistic children don’t always follow this pattern because they have trouble with empathy.

Researchers at the University of Tokyo’s Department of Cognitive and Behavioral Science wanted to explore a different angle on it. They believe the answer might instead be that children with autism spend less time looking at other people’s faces and thus miss the fact that somebody is yawning.

To test this they ran two studies where groups of children with and without autism looked at videos of people’s faces while wearing eye-tracking devices. In one test they were shown the top of the face, including the eyes, while in the other they were shown the bottom of the face, including the mouth. To avoid tipping off the children that yawning was the issue, they were told to count the number of people wearing spectacles or having beards.

To test the visual cues theory, the researchers set the system up to have the screens show a static image of the faces. The yawning animation only began when the eye-tracker confirmed the child was looking at the screen.

As expected, the group as a whole was much more likely to yawn while watching the animation than a static face. However, it turned out the “yawn rate” was consistent at around 30 percent regardless of whether a child was watching the eyes or the mouth, and regardless of whether the child had autism.

With several previous studies suggesting children with autism are much less likely that those without to “sympathetically yawn” in social settings with real interactions, the researchers believe it’s possible that “it’s not an inherent lack of empathy in children with autism that’s to blame for their lack of social yawning, but rather their inattention to facial cues.”

(Image credit: Maria Cisternas via Creative Commons license)