Unilateral "smiles" are almost always not smiles at all. The vast majority of what are perceived of as one-sided smiles are nearly always either (in decreasing order of frequency):
- An Insincere Smile
- A Signal of Regret
- A Contempt display
However this particular asymmetric expression exampled by A-Rod (during 1:12 - 1:20 in the above video and captured at 1:14 in the images below) is an important exception, because a Sincere (Duchenne) Smile can be either:
- A partially Suppressed Smile of Joy-Happiness or
- A Sincere Smile in the initial or end-stages of its expression
Can you tell the difference between the five different emotions?
We cannot see A-Rod's forehead, but in this moment it would show no dynamic contraction. Thus there may be very mild horizontal lines on his forehead associated with simple aging (A-Rod is 38), but no furrows consistent with muscle contraction.
While the left corner of Rodriquez's mouth (our right) is contracted laterally, the primary vector of its motion is upward. The left cheek muscle is contacted upwards pulling the corner of mouth up with it. Notice only A-Rod's upper teeth are visible.
Alex's left eyelids are partially closed. This is an absolute requirement for a Duchenne (Sincere) Smile. Along with this partial closure, there is a dynamic (temporary) concave-up furrow created in the lower left eyelid - while not present on his right. This is due to contraction of the outer portion of the eyelid closing muscle [orbicularis oculi (pars orbitalis)].
Alex Rodriguez was feeling emotional dissonance - here the competing emotions of sadness and then happiness. Thus A-Rod's expression of joy, and his sincere smile, was for these moments naturally suppressed.
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