«Our study demonstrates that dogs can distinguish angry and happy expressions in humans, they can tell that these two expressions have different meanings, and they can do this not only for people they know well, but even for faces they have never seen before,» says Ludwig Huber, senior author and head of the group at the University of Veterinary Medicine Vienna's Messerli Research Institute. (sciencedaily.com)
[3] The results showed that women with happy expressions were seen as more desirable. (ahealthblog.com)
It was also found difference in between processing happy expressions and neutral faces at the right superior temporal gyrus, left cuneus, right middle Occipital Gyrus, right inferior frontal gyrus, and right Lingual Gyrus. (cogneurosociety.org)