Question: **Is there any evidence which shows whether users are more able to recognise another user's Photo over their Username or vice versa?**

I am interested in understanding this from a usability perspective.

Lets say on a site such as this network, a user has both a username as well as a photo/avatar.

* On *Sci-Fi.se* [DVK](https://scifi.stackexchange.com/users/976/dvk) has a very recognisable **avatar**
* On *StackOverflow.se* [Jon Skeet](https://stackoverflow.com/users/22656/jon-skeet) has a very memorable **username**

Which of these is more recognisable/memorable?1

i.e. If **DVK** was to change his picture2, would this throw users off (not quickly recognising who the post if from) or would there be more of an issue if **Jon Skeet** changed his username?3

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**1.** Lets ignore rep points, as it is not relevant to my question.  

**2.** The caveat here is that 'DVK' is also a memorable username, but for the sake of this example lets ignore that.  

**3. Please reference research where possible.**

Answer: 
As most people have said, it depends on the user.

For me personally it depends entirely on the context.

* On forums I'm heavily dependant on usernames for identifying people. I tend to remember people by their usernames on forums (and here). I think this is because forum users tend to use avatars detached from their identity such as cartoon characters or memes.
* On Twitter and Facebook I'm heavily reliant on the avatars of users because those people tend to represent themselves by their own face. I either learn what they look like (if i don't know them personally) or if it's someone i already know from the real world I know their face.

I So my answer would be think about the context of use and base your decision on that.
Although it is not exactly about avatar and user name, there is a research paper about distinctive file icons called [VisualIDs: Automatic Distinctive Icons for Desktop Interfaces](http://scribblethink.org/Work/VisualIDs/visualids.html) in SIGGRAPH 2004. Visual distinctiveness is unsurprisingly useful for both short term memory task (browsing for a specific file) and long term memory task (sketching and describing icons two days later). One interesting principle is that arbitrarily unique icons can be recalled regardless of their contents or meanings to the user. 

Note that this research assumes a priori that "Search and memory for images is known to be generally faster and more robust than search and memory for words" with a reference to [Data Mountain (UIST 1998)](http://research.microsoft.com/apps/pubs/default.aspx?id=64329). Despite no direct comparison to textual memory, I believe that this research can supplement that visual memory is *stickier* i.e. changing a distinctive and registered avatar would throw users off more than changing a username.