What makes us yawn? | HowStuffWorks
https://science.howstuffworks.com/life/inside-the-mind/human-brain/question572.htm
WebSep 11, 2023 · Yawning is an involuntary action that causes us to open our mouths wide and take a deep breath. We know it's involuntary because we do it even before we're born: According to Robert Provine, a developmental neuroscientist at the University of Maryland, Baltimore County, research has shown that 11-week-old fetuses yawn.
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