I doubt they'll ask, because GRE scores are more used to weed people out before interviews. If you've already gotten one, clearly they decided it's not that big of a deal, and they'll probably be much more interested in hearing about your academic and research backgrounds, and your interests and plans.
If they do ask though, I would very simply say that you did not do as well as you were expecting/hoping, and that you feel that your GPA/research/whatever far more accurately represent your abilities and potential (and possibly elaborate more on those things). Or something like that.
nerves! i dont know if you want to say that, but in my case the whole situation makes me freak out. my heart rate is way elevated the whole time. at the end of the test, the score said 700 but if it said 439 1/2 i would have believed it.
you could consider mentioning that you dont test well in that kind of situation - math under pressure, requiring you know the "trick" rather than knowing how to solve the problem longhand.
Actually, it is possible that they would ask a question like that. You never know exactly what they're going to ask. I will say this--don't lie about it. You could mention that you expected a higher score because of your amount of preparation. Do NOT say that it was because you got a rotten test or because you are not good at taking standardized tests (obviously you are not, but I hear that excuse for "subpar"--but in reality, quite good--scores constantly from other students). If they do ask and push you on it, then I might say that you expected a higher score and that your research accomplishments/GPA/etc. are a better indicator of what you are capable.
At the interview point, though, professors and students are going to be looking for a confirmation that your research interests can fit within theirs and that you are not a cocky, arrogant, unsociable jerk. 99% of people will do just fine if they act "like themselves"/normally. Be prepared, but don't be intimidated--once you make it to the interview, the playing field is level. I come from a modest educational background in terms of my alma mater's national prestige and I was able to "beat out" at least one person from Ivy League schools at interviews. You'll find that some of your fellow interviewees will seem like they might stab you in the back with an icepick when you turn around, while other interviewees will be friendly but competitive. You will want to fit into the latter category.
Basically know your own research and your interests like the back of your hand. Also, for the professor to whom you are applying, thoroughly know the generalities of their research and some of the specific aspects. It helps if you are able to say, "I really liked the way you ________ when you were considering [whatever construct/specific part of the construct was being examined]" and stuff like that. Tie your research into theirs. At the same time, don't be so comprehensively prepared that you are citing the prof's obscure 1973 article published in the Eastern Appalachin Journal of Translational Neuropsychology. Or tell the professor that they are your "research soulmate". I've heard that one and it didn't work out too well, obviously.
Be prepared, act like yourself, be friendly but very focused on the task at hand. And most importantly don't obsess over the details. You'll do fine. Remember, they aren't going to try and trip you up. And if you happen to say something that you think is kind of dumb or can't answer a question, then don't fret--I had a couple of those moments and many people do. And I was fine.
And unless it's completely obvious that it's okay or encouraged do not drink alcohol at any dinner/function.