In the above video, Natalie Portman demonstrates a common nonverbal gesture - and yet one rarely described. In body language parlance, this is but one of many examples of what is known an "illustrator" - for they serve to illustrate, emphasize and add description and flavor to verbal language.
In this interview, Natalie is recounting her research of, and preparation for a rendition of "Iko Iko" with Sia, Jimmy and The Roots. During the segment from 1:07 to 1:12 as Ms. Portman says, "... Yeah - it said something that it was like Creole, like the king being [Fallon over-talking] - a Mardi Gras, yeah, Creole ...", her hands move in an elevated, open palm, moderate-to-high frequency, moderate-to-high amplitude gesture. When interpreted in toto (particularly with Natalie's facial expression), this nonverbal is a "Kinda-Sorta-Maybe" gesture illustrating a "Nebulous quality" and a "Searching for the Correct Description" to that which is being discussed.
In this particular example, Natalie Portman's body language is highly congruous with her verbal language (as well as her paralanguage) - thus her sincerity quotient is very high. However this gesture is often used when the verbal language is (when simply taken at face value) decisive and definitive - yet in such a scenario, if you know what nonverbal signals to look for - you'll pick up on the insincerity. Often times our subconscious detects this disparity and leaves us with a feeling of ill-at-ease or "something's not quite right here" emotion.
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