OMG…I just do NOT believe it when men say this. 
I am always thinking of SOMETHING at any given point in time. So no…dont tell me you’re not thinking anything. Why cant he just say it? 
What are you thinking dammit? 
Our thoughts are too complex for women to understand and comprehend.
Or the guy is thinking about the girl herself when this question is asked so he’d rather not say that or give that as an answer to the woman 
Oh yes...I forget how complex a man's mind can be. Absolutely.
I mean, its got to be difficult you know...watching TV...eating...burping and of course repeating all of that.
Hats off to you all.
Re: Girl: What are you thinking? Boy: Nothing!
See, I know that there are moments when I’m quiet…and I’m really not thinking anything, lol. I’m too tired to think…and I’m just staring off into space or taking a break.
I do think that it can be courteous to ask either gender what they’re thinking from time to time. It can reflect concern…a need to make sure that the person is okay…that you haven’t unknowingly said something tactless, etc. But again, all things in moderation. This is also one of those questions that (while the intentions behind it are in the right place)…can get really annoying…if it’s oft-repeated. And I think that people who are more introverted especially can be irked by it. I’m overall an introvert…and I get a bit annoyed when my family (dad, or cousins, for example) ask me why I’m quiet…or what I’m thinking…and when I say “nothing”…it’s followed by “how can you say nothing?”…or assume that I’m upset or worried 
Seriously…I’m not always thinking about something, 
Re: Girl: What are you thinking? Boy: Nothing!
I actually , infact i have been told all men are capable of simply thinking about nothing, it bothers the living crap outta Hiba when she comes and says what are your thinking and I actually respond with a "HAAN" :D
Re: Girl: What are you thinking? Boy: Nothing!
It's opposite with me. What you thinking? NOTHING. Which basically means, I am thinking about something, I just don't wanna tell you.
Re: Girl: What are you thinking? Boy: Nothing!
the boy is probably picturing the girl naked.
and if he says it, he gets haww hai's and ewws (just like this truthful post will)... so his response: "nothing"...
Re: Girl: What are you thinking? Boy: Nothing!
^men are too selfish to even be thinking about a girl naked, they’re probably thinking about sunday nights football game, or a stupid playstation game 
Re: Girl: What are you thinking? Boy: Nothing!
Boys can't sing
Re: Girl: What are you thinking? Boy: Nothing!
Its because they don't want to answer all the questions that will follow when he tell you what he was thinking....
Re: Girl: What are you thinking? Boy: Nothing!
^ yep.
That is the sign of imminent war.
Better say nothing and 'act' as empty-minded. ;)
Re: Girl: What are you thinking? Boy: Nothing!
NOTHING = Thinking about some other girl 
Ok now we can’t tell you THAT . . . Isn’t it 
Re: Girl: What are you thinking? Boy: Nothing!
we are thinking of so many things at the same time that when somone asks we forget what we were thinking about.
Re: Girl: What are you thinking? Boy: Nothing!
well, from what i've heard, "nothing" in a man's case really means 'nothing'........or maybe they dont wanna talk about it
Re: Girl: What are you thinking? Boy: Nothing!
most of the boys think
"how peaceful it is now that she is quiet"
but nah, you girls cant take it and open your mouth "what are you thinking?" ! duh!!!
rest? they think how pretty their wife/gf is but problem is if they tell their wife/gf tu uss k nakhrey hee khatam nahi hotey...
Re: Girl: What are you thinking? Boy: Nothing!
Men have only one thing at their mind all the time so they cannot give you an honest answer.
Re: Girl: What are you thinking? Boy: Nothing!
Oh my god.. i hate when my hubby says this to me.. So I do the same thing now. i ask him once and if his reply is nothing I observe complete silence with him till he gives up and asks me what's wrong or some sort of question to which I answer "nothing".
Re: Girl: What are you thinking? Boy: Nothing!
Baychara husband .
Re: Girl: What are you thinking? Boy: Nothing!
most of the time i think nothing which is really not appreciated by my mother.
Re: Girl: What are you thinking? Boy: Nothing!
I think for men "nothing really does = nothing.