oh dear, i have asked that question. you have to understand that sometimes your face does things that aren't connected with what your brain is doing (i think there's another bit of you that behaves the same way) sometimes you have very loving / lustful expressions on your face, which may or may not be associated with your thoughts. we would like to think that the loving / lustful expression is in some way connected to us. however your answer is normally "nothing" and we find it very hard to believe that you could have absolutely nothing going on in your head. from that we then assume that you're hiding what you were thinking... the lustful expression was obviously to do with kylie's bum / some girl from work / something even worse and by this time you are just looking guilty and oh boy are you in trouble then. i would suggest that a good answer to keep in stock might be "i was thinking what a nice bum you've got", failing that, say it was football / dinner / sex...you might look like you haven't got much imagination, but it's better than looking guilty...good luck (the nice bum comment will please the most suspicious girlfriend)