Who Smiles More at Princeton?

Via a link found at misbehaving.net ("Well-behaved women seldom make history"), I found this picture.  It is a set of computer-generated average faces of students at Princeton.  The one on the left is the average man; the middle, the average student; the right, the average woman.  The images on the bottom are "processed representations of differences between faces which are used in algorithms".

I had to shrink the picture a bit in order for it to fit.  The differences are more apparent when viewed at full size.  It appears from this, that Princeton women smile more than Princeton men.  Princeton men pout a lot.  Why is that?

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Every time I pose a new question here, I will answer the last one.  The last one was: Why did I wake up with the song, Girls Just Want to Have Fun, playing in my head?  It's because before I went to bed, I had gotten a phone call from my wife.  She had gone to Ohio with her mother and sister.  They went to look at pottery and fabric, for their various hobbies.  They ended up getting lost, would be late getting back, and I could hear all kinds of joking and laughing in the background.  I never knew that getting lost could be so much fun.