Brie Larson was a guest on the Tonight Show last week. The actress/singer recounted for Jimmy Fallon a time when, as an eighteen-year old, she went to a college party at Brown University. During her description of this misadventure, she displays one very telling body language signal three times.
When a woman adjusts her hair with her elbow up and out - with her upper arm approximately in the same plane as her "shoulder axis" - there is a high degree of reliability that she is putting herself on sexual display. Here Brie Larson is showing us an armpit display during 0:01 - 0:04.
As is the case with many nonverbals - the true emotion (sexual) is (partially) camouflaged with a very obvious and practical action (e.g., here, a false hair adjust). And while this is absolutely an alpha display - be careful not to confuse this with the "Hair Adjust Behind Ear" (HABE) nonverbal.
It may very well be in a voyeuristic sense - e.g., if televised, on YouTube or social media, etc. - she is putting herself on display for the public-at-large rather than necessarily for the person who is interviewing/speaking directly with her.
When there is a more direct sexual attraction - such as in a semi-private setting (e.g. at a restaurant) or in private, the elbow is typically held up for longer duration. Crucially, this sexually provocative nonverbal configuration exposes the arm pit as well as putting the breasts on deliberate display. When the sexual attraction is at a higher level - sometimes this armpit display may be seen bilaterally (with both arms).
While this very flirtatious body language tell is significantly more commonly with women - it's certainly not rare at all to see it exhibited by straight men.
As with all nonverbal communication - it's of paramount importance never to interpret signals in isolation - but together with other simultaneous (or nearly so) signs clustered with it. What are some scenarios where the armpit is exposed in which a completely different emotion is being broadcasted? (And just as importantly - what are the other nonverbal modifiers one would expect to see in such circumstances?)
A second armpit display: 0:35 - 0:39
Again during 0:56 - 1:00
Nonverbal Communication Analysis No. 3337: Barack Obama regarding Vladimir Putin on 60 Minutes
Nonverbal Communication Analysis No. 3268: Advice to the Ten Republicans for Thursday Night's Presidential Debate
Nonverbal Communication Analysis No. 3258: Hillary Clinton speaks out on "inaccuracies" of private email controversy
Nonverbal Communication Analysis No. 2177: "I'm Tired of Bronco Bamma and Mitt Romney" - We're all Abigael Evans Dialing up her Alpha