In his final all star game last night, Derek Jeter went 2 for 2 with a lead off double and a single.
IThese two images may look similar - yet from a nonverbal point-of-view there is an important distinction to be made. In this first image, the Yankee Shortstop has the all the components of a true sincere (Duchenne) smile: a relaxed (uncontracted) forehead, partially closed eyelids, a dynamic and concave-up furrow in the lower eyelids and upward-vectored cheeks.
Sincere smiles which are suppressed may have (surprising to many) a closed mouth and not even show any teeth. Yet in full and sincere smiles when the teeth are seen - only the upper ones should be visible - with a few exceptions: The lower teeth may be visible during a sincere smile if the line of sight affords such an angle (e.g. a camera looking downwards or a tall person looking down at a shorter person may see their bottom teeth). Additionally, if a sincere smile is held too long, fatigue sets in and the lower teeth may become exposed.
The lower teeth are also very often exposed in the context of sincerity - if there is a component of true laughter (although the other components of a smile laughter also must be present) - as the Captain of the New York Yankees shows here.
It is extremely common to see the lower teeth exposed and even very over displayed during insincere smiles (see: Nonverbal Communication Analysis No. 2546: Miss America Nina Davuluri, A Beautiful Woman - but What of Her Smile?)
Nonverbal Communication Analysis # 2312: Bruce Willis' Body Language - Contempt vs. Suppressed Smile vs. Pseudo Smile vs. Sincere Smile
Nonverbal Communication Analysis # 1905: Ann Curry's Smile and Sincerity Quotient
Nonverbal Communication Analysis No. 2482: Alex Rodriguez's Sincerity Body Language of a One-Sided Smile
Nonverbal Communication Analysis No. 2868: Queen Elizabeth II, Lena Headey, Game of Thrones and Body Language
Nonverbal Communication Analysis No. 2515: Eliot Spitzer vs. Scott Stringer Insincere Smile with Anger Component Body Language and the NYC Comptroller Race