Male, 15/20. Fairly even mix on my misses, although 3 of my misses I was inclined to go the other way at first, then talked myself out of it (numbers 5, 7 and 12).
female 19/20
it is all in the muscles around the eyes.
But I am cheating, I already knew that - one psychology class I took had a small segment in reading the face and body for clues.
Male 13/20
Male. 15/20 correct. I missed 3 males and 2 females. Answered “The eyes” at the end. Made me happy I knew what was missing, but disturbed that 25% faked me out 
female, 17/20
It’s in the eyes.
Female, 18/20. I missed 13, thinking it was maybe genuine, and 15, thinking it false. (I’m not sure of the gender of 13, to be honest, but 15 is a male.)
The eyes have it.
16/20 - Male
I missed 2 female and 2 male. Two of those were fake and two of those were genuine.
Female 13/20
I told myself to look at the eyes but ended up looking at the mouth. Clips were fast and I suck way worse than I thought.
16/20 Male.
All the ones i missed were genuine, that I thought were fake. Though I did have 2nd thought about 2 of those.
Jeezus! What’s with the meth users in thar? I found myself worried that some of those folk needed a good rehab program more than they needed to be taking part in a fake smile test.
15/20, female.
M -12/20 
F: 19/20, judged strictly by amount of eye-crinkling.
19/20 Male. Number 17 was the one I got wrong.
I’m hardly one to judge, but my word there were some, … ah …, unusual looking people in that group.
Edited to add: I mean I scored 19/20 and am male. I’m not 95% male. 
Male. 18/20. Mistook 4 and 12 as fake.
I concentrated on expressiveness of the eyes, particularly ‘eye crinkling.’
16/20. Only looked at the eyes & not the mouth, but still not a perfect guide for me clearly.
Missed the fourth person from the end of the quiz (# 17); I was pretty indecisive about his smile.
Olives and others pretty well nailed it with her reference to the eyes, but don’t forget other parts of the face.
I wonder if the person’s appearance had any effect on test answers…
18/20, female. Missed 11 and 17.
18/20, female. It’s the eyes for me too. I missed 15 and 17 since I labeled them as fake. Looks like I missed the two guys that were missed the most often. They were much more subdued than the other genuine smiles.
17/20, woman. I thought one genuine smile was fake, two fake were genuine. Eyes and head movement are the key but there were some tricky ones in there!
16/20, female. I missed one fake and thought three genuine were not.