0.001 response time HDTV.. is my ps3 lagging or is it just my mind ?

I just got a new LG 50'' Plasma HDTV and connected my ps3 to it using a HDMI cable.. for 2 weeks i believed it was completely perfect and no lag and stuff also putting in mind that it has a 0.001 response time which should be completely HD lag free.. later on i removed the HDMI cable to take it with me to a friend.. when i came back i plugged it back in to my LG tv and begin thinking that there is somekind of lag.. maybe it's just my mind messing up with me..

So is there anyway that i could measure if there is lag or not once and for all so i would be completely sure of what's going on ? Maybe there's some kind of absolute way just to be extremely sure of this.. and can companys claim that the tv has this response time while it's not real !? I actually read it in its specifications on the cover !

turn on "game mode"

it might be your ps3. games lag sometimes on psn

Perhaps your friends tele is superior to yours?

It sounds like your PS3 must be fine, so it has to be your mind Lagging.iamdanthaman