I wear my hoodie (hood on a Jacket) every day. Apparently, when a person's brain temperature becomes too elevated, it triggers a yawn to cool down the brain. So I ask, do you think wearing a hoodie a lot elevates the brain temperature?

http://www.aoma.us/PDFs%20and%20Docu...ampionship.pdf

Yawn coming on? Go ahead, rev up your brain - Chicago Tribune

What little I have read on it, it appears it is talking about "cooling" your brain is from use, not outside temp. More of an internal temp the comparison of a computer, when in higher use it gets hotter.