What I've found, and I don't know if it is social conditioning or just too much testosterone, is that as a man, I don't deal with my emotions vocally. Women, on the other hand, deal with their emotions almost entirely vocally. (at least, from a male perspective.

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What this means for relationships is that when a man goes off to think, the woman thinks that something is seriously wrong
with her, and that is why you aren't talking. What is the natural reaction for any human when they're accused of doing something wrong? The safest answer is "get defensive."
So here you come, back from thinking, with new ideas swimming through your head, and all of the sudden, she's defensive, and you can't figure out why. She honestly believes that you've been holding something against her, while you were just off working through a problem that most likely has nothing to do with her, right?
So, how do we fix this? Well, if you believe all of the relationship books written by women for men, the answer is to share your feelings and be sensitive... Tell me, women... How many of you are actually attracted to a 'sensitive' man? Sure, it's nice at first... but then he seems too clingy... and he's just not 'rugged' enough for you anymore, right? Also, aren't you tired of having to listen to all of your girlfriends' problems, so why should you have to listen to your man's problems?
Here's the answer to all of this, short and sweet...
Keep being a man. Keep going off and brooding, but let your girl friend know that you just need time to think about a problem, and let her know that you're not brooding about her. While you're mulling over things in your head, be available to listen... Women want nothing more than someone to listen to them without having to share equal time listening to someone else's problems. She will notice and appreciate this one small change... simply take the time to let her talk.
Also, for those women out there... when a man says that nothing is wrong, yes, it is a lie... but unlike you, it does not mean that he wants you to fish it out. If he wanted your help, he would have asked for it before you noticed that something was wrong... Guys are bull-headed like that, (I'm certainly no exception) but if you want to make him happy, give him his space so that he can work the problems out... If you leave him alone, he will come back invigorated and ready to tackle any problems that comes his way.