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: 
To the other questions I would add accessibility concerns. For many with poor sight a username is much more easily used either by using zoomed text or some for of text reading. Even for those who don't need screen enhancements (e.g. me) avatars can be hard to tell apart e.g. Twitter and using pictures, may are difficult to tell who they are as photos are not well taken or the user is trying to be clever and show something which works on a reasonably sized photo but not a thumbnail. 

Given that last thought I would add a concern about general differentiability it is much easier to make two avatars very nearly the same and not notice compared to usernames, if the users are trying to confuse people - which some will do.
Certain avatar images are very memorable and distinct. Some are almost indistinguishable. Likewise with user names. Someone who was asked to remember the username of "Jon Skeet" and was asked a day later later to identify it from a list of the ten most similar usernames might have a good chance at identifying it, while someone who was shown a generic gravatar and asked to identify it from a list including nine randomly-selected ones would have a relatively poor chance even five minutes later. On the other hand, someone asked to remember a username written in an unfamiliar script [e.g. a hypothetical user "絕對沒有"] would have a hard time than someone asked to remember the gravatar of Jon Skeet (sompared with the ten most similar gravatars, assuming nobody copied Mr. Skeet's picture). The differences in memorability between different usernames and avatars would seem to outweigh any general advantage usernames would have over avatars or vice versa. Incidentally, without looking back at the previous hypothetical username, can one one remember whether it was "絕對伏特加", "絕對沒有", or "絕對值" [Chinese characters from Google translate]