In this recently viral video, Lance Kale Jackman fires a handgun in the family living Room (It's not clear whether this was a blank or live round). His brother, shocked, then yells, "This is why mom doesn't fucking love you!"
From a body language perspective, this 9.1 second video provides a great illustration of a particular nonverbal signal known as an "Inward Lip Roll". The inward lip roll (aka ILR) is one method the psyche uses for both the inward down-regulation of, as well as the outward suppression of an emotion which, either momentarily or of longer duration, he/she does not want to be discovered or fully expressed. Most of the time an ILR is suppressing a negative emotion (anger, disgust, etc.). However here the emotion being squelched is joy/laughter - albeit in a considerably atypical scenario.
Mr. Jackman is about to fire a revolver - an action of which his brother is yet unaware.
His lips are rolled inward in an effort to try and suppress his joy-laughter. An ILR involves the teeth biting down on the lips (sometimes gently, sometimes with significant force). Note his mid-face is taught - which is easily seen in his "mustache area" and flared nostrils.
The instant he fires the gun, Jackman's inward lip roll begins to rapidly disappear - for he no longer has the need to keep a secret.
Lance Jackman begins to break into a full laughter. Notice that his blushing, which was also present earlier - is now more fully expressed.
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