Mistook new faculty member to be a student, how big a faux pas is it?

I'm a female professor in my late 20s and I'm pretty sure I look even younger than I am. I've been mistaken for a student a bunch of times and it's always been an honest and totally understandable mistake. I'm often assumed to be a grad student; heck, I discovered in front of my mirror three days ago that wearing the school logo T-shirt I somehow acquired is inadvisable because it makes me look nearly indistinguishable from an undergrad.

I know doing this is embarrassing for the person who messed up, but looking at me and concluding that I'm very likely a grad student is reasonable and something I know is going to happen unless I'm wearing a fancy-schmancy suit. Heh! I've even done it myself. One time when I was meeting a (male) colleague, each of us mistook the other for a grad student; we've been teasing each other about it since. The only circumstances under which this would bug me would be if the person doing it were trying to be patronizing, or covered it up in a way that introduced some creepiness.

But yeah. I'm accustomed to it and I know my status surprises people. When someone asks if I'm a student, I laugh it off and say, "I am a very young faculty member." Most of the time thereafter I forget it happened. You did everything you needed to in order to make amends; I'd say put the guilt aside and move forward with a professional relationship with your colleague.

Don't worry (too much), I think this happens to everybody at some point in their academic life. Your case isn't even particularly egregious, given that the new faculty member just started as an assistant professor, so likely she actually was a grad student not very long ago. I once idly asked a fellow conference attendant who she is working with, and she told me that she is a tenured associate professor. Embarrassing? Certainly, but not the end of the world. You apologize and move on.

The problem is that the person who I was introduced to is female, and I am afraid that I might have offended her.

I am not sure whether being female makes her more or less likely to be offended. However, I can't help but notice that most such stories are about female professors, so it seems to me that we jump to conclusions about them more freely than for males (or we guys just have trouble assessing women's age accurately). In any way, I have learned my lesson to be extra-careful before assuming that a young-looking female academic is a student, and you should too.

Am I just being paranoid or will some people really feel offended from such a comment?

I would not worry too much. You can bring it up lightly on a good ocassion and apologize, if such an ocassion presents itself in the next weeks. However, don't make it a bigger deal than it is, and if she seems unbothered or hasn't even noticed, then let it go.

I've been in similar situations, and I think there's one clear way to handle it. After you inadvertently underestimate someone's level of expertise or qualifications like this, the next thing you do after a quick apology is express interest in their work as a professional.

In this case the obvious follow-up questions after a brief apology look like:

• "What's your area of expertise?"
• "What are you researching?"
• "Any advice for me? I hope to be on the job market soon."

Then continue with as genuine interest as possible. In short, the way to rectify accidentally treating someone like they're not an expert is to then treat them like the expert they are.