A new study shows that children with selective mutism are more chronically over-aroused than children with social phobia alone. Although they outwardly appear similar to their social phobia counterparts, kids with sm struggle with a constant alertness more often than other kids.

In the study led by Deborah Beidel, Ph.D., ABPP, children with sm and children with social phobia were tested while playing the Nintendo Wii, with a device that measures skin conductance (like what a lie detector looks for, or what an ‘e-meter’ from the Church of Scientology measures – when something affects you emotionally, it responds).

What Beidel found was that internally, sm children struggle with a constant storm of activity, more so than kids with just social phobia. This was found to be true not only during the social interaction, but they were also on edge before it in the waiting room with their mothers. Whereas the kids with social phobia could relax a bit, the sm kids were stuck in a higher state of alertness for a longer period of time (sort of like a mild adrenaline rush that doesn’t wear off until you get home).

But the sm kids looked fine on the outside. This is because the avoidance of speaking acted as a way of lowering their own anxiety, leading Beidel to conclude that children with sm are better at regulating their emotional distress, i.e. looking calm.

Also, most of the kids with sm used physical avoidance to manage their anxiety further. When asked to play the Wii with their peers, many stood slightly behind the line of Wii players or slightly closer to the tv than everyone else (to focus their attention on the game), possibly as an unconscious way to lessen their levels of discomfort.

The details of the study can be found here.