A study of the facial expressions of minifigs measured whether they are grumpier now than in the past. And it questions whether this makes a difference in a toy for children.
Check out the article describing the study at:
http://usnews.nbcnews.com/_news/2013/06/11/18904238-do-legos-need-anger-management-figurines-grumpier-than-ever-study-says?lite
Wish I had been able to do research on minifigs in my earlier life as a professor! Sounds like a dream job, eh?