I'd be interested in seeing whether showing your (or, well, someone's)
real-world face and/or name tends to make people treat you more
courteously than a default Gravatar, or whether there seems to be no
Unless you make it into a double-blind trial - which means posting the same questions, answers or comments by users with and without pictures, so you could compare reactions, which would be rather tricky as it would duplicate content - you'd only measure correlation, and correlation is not the same as causation.
Even if it was proven that users who show their real faces tend to be upvoted more than those who never bothered to upload pics and still use identicons, we wouldn't know if they are upvoted because of that.
It is not unlikely that the use of real pictures vs. identicons is correlated to other factors, such as
whether you plan to participate in the forum in long run or only want to get a few technical answers
whether you are naturally more inclined to form social relationships (and therefore have a habit of posting your personal pic everywhere you can), which reflects in your communication style
I guess this would make sense only when comparing among new users with
or without gravatars. (new = less than x amount of rep and/or time on
If there's 10 new users who uploaded pics (someone who does this straight away exhibits an even stronger motivation to do so than somebody like me - if I recall, I didn't upload my picture until I'd already used SO for a few months) and 10 users who didn't, I bet you there's already something different between the latter and the former, in terms of their personality type and what not.