Practical Applications for Nonverbal Intelligence and the Emotional Indicators of Sudden Jaw Movements.
Most of us are familiar with the term draw-dropping surprise—the mouth agape with teeth showing. This behavior is a reliable indicator that someone has truly been caught off guard, has lost their way, or may even be terrified.
But what about a jaw shift? What does it look like and what does it indicate? Suppose you’re talking to someone and suddenly it looks like they were punched in the side of their jaw, which suddenly moves sideways and then snaps back. Sometimes people will repetitively shift their jaws from side to side as soothing behavior designed to mitigate stress. But other times it has different implications. See below.
Former FBI profiler and body language expert, Joe Navarro, writes “Jaw displacement or repetitive jaw shifting (from side to side) is an effective pacifier. This is also simply a compulsive behavior in some people, so note when and how often it occurs and look for other confirming behaviors that something is amiss. Most people do this infrequently, and thus when you do see it, it is very accurate in communicating that something is bothering them.” 
A Telltale Sign of Stress
Sudden jaw movements are often very visible, even via video conferencing. When you observe it, do not ignore it. At Merrill Research, we see indications of sudden jaw movements in qualitative studies when someone is struggling to grasp a new product concept, for example. And when we see this behavior, it is always an opportunity to probe and learn more. If you see this behavior, then you might follow up with a question asking the person if they have any concerns or if there is any confusion. Dig deep enough, and you will find out that there is.
Most Communication is Nonverbal. Are You Fluent?
 The Rutledge Dictionary of Nonverbal Communications, s.v., “Jaw Droop,” Routledge, 605 Third Avenue, New York New York 10158
 The Dictionary of Body Language, Joe Navarro: https://books.apple.com/us/book/the-dictionary-of-body-language/id1281489160.