Why do I stick my tongue out when I am concentrating?

Do you have something you do that happens without you really paying attention? My SO pointed out that I stick my tongue just a bit out whenever I am captivated by something I am doing, whether it be painting or trying to fix something.
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+1 y
I also have found that once I am aware of it, I lose a bit of concentration
Why do I stick my tongue out when I am concentrating?
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