Dishonesty is pretty common, besides as a defence or a persuasive tool, some times it is used to avoid situation or to protect the person they are lying to. I think people try to calculate things like this when they are getting to know you, repetition makes the motivations obvious.
oxymoron much? :P
I react to what they've said, especially if it's clear they've meant something else and then when they pout about my reaction, I tell them "Well, you should've said what you meant and meant what you said."
Well... one person can't do both of those. So to which of the two am I responding?