This is a darling video and fun to watch. From a nonverbal point-of-view it illustrates some excellent examples of body language tells fundamental to all human beings.
The eyelids open very wide in a primal expression of surprise when this little one initially hears the lion's roar.
A surprise mouth may be characterized either by a vertically oriented oval mouth - or as seen here - a slightly opened relaxed-appearing mouth (aka "slack jawed" appearance).
When the lion roars again, this little angel relapses back into eyes that are "white and wide" with more slack jaw of surprise.
This time the emotion which supplants surprise is joy - manifested here by laughter.
With the exception of psychological shock (e.g. watching or hearing about a severe care accident, an unexpected death, other major life events, etc.), when the expression of surprise lasts longer than just a few seconds - it is being acted out or exaggerated upon and thus is a form of deception or insincerity.
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