As you can see, there's not too much to be found on the subject, at least not to any impressive degree. Understandable, since presumably there are better and less nebulous things to conduct studies on, but I thought it would be interesting to see how my friends' profile pictures would compare against these trends discovered by others in larger studies. 

I would say that the results of my analysis were surprising, although I do stress again that it is only a very small sample and not very representative of any significant social circle outside of mine. I don't particularly have a hypothesis for the trend in this analysis, except perhaps that having only oneself as the subject in one's Facebook profile picture is overwhelmingly common and that simply made it more likely for extreme values to be present in that category.