Responding to a request, this article hopes to answer the question. The answer is cultural as much as biological. I've also sought to connect with the issue personally. Those who know me well know I crave talking deep stuff, but I was not always like that.
Until I lost my first marriage I had the capacity to go deep in discussion, but little interest. And it did not go well for me. It's part of the reason my first marriage failed. As I look over my journals in that period of life I certainly was reflective. So why did not I open up with my then wife in the latter period of that marriage? I was busy, distracted, unstimulated at that point of my life, and really did not think there were any problems worthy of discussion. I'd become blind to my own circumstances.
Culturally, baby boomer men (born between 1945-1960) do not reflect about deep stuff with themselves, let alone talk with others. There are exceptions. They grew up in a challenging and confusing time. Perhaps it's more accurate to say they think a lot, especially as life's transitions confront them. This can be frustrating for their wives, who see them shut in, who resist 'help'. The more a wife may want to help, the worse the husband feels the pressure to give what he may feel incapable of giving. He may feel he can not give her what she wants, and he may be right.
Gen-X men (born between 1961-1981) are probably a little more amenable to expressing their emotions, but do not forget who their fathers are – baby boomers. They've had to learn how to do it, and some, like myself, have had to learn the hard way.
I read an article by Gail Sheehy, and she said that men do not understand women, and they know it, yet women also do not understand men, but they do not know it. Hence, why women are trying to work their men out, and why men do not tend to bother. Another issue that Sheehy mentions is men do not seem to ask questions as much as women do. We've been trained by our culture to work things out for ourselves. Our biology, too, because we're the 'stronger' gender, causes us to think we've got to work it out for ourselves. No wonder we're telling ourselves to man up instead of open up. And little wonder men seem less inquisitive than women.
Interestingly, the cultural scales are sliding and more young women are working things out for themselves; young men can be the ones asking the questions.
Advice for women who feel they can not reach their husbands. Back off. Do not make it a sport. Ask better questions. Questions that do get him talking. Work into the discussion from there. Understand that he will engage if he knows how to. Time discussions appropriately when he's not distracted by something he thinks is more important. And, accept his simple answers. Do not get frustrated by them. And if he feels you're satisfied with his answers, he's more likely to keep going.
I find I open up when I'm stimulated, when there are no other distractions, and when I know I'll be listened to, and most of all when I've got something to say.
Intimacy is central in all this, yet …
Intimacy is a vague concept in marriage. Clarity comes when both partners can agree what it means.