It's time, says San Francisco sociologist Lillian B. Rubin, to do away with the notion that it is women who are dependent on men in marriage and consider that it could be the other way around. We have, she believes, mistaken men's economic independence for emotional independence.

"Whether men are 25 or 55," she says, "women usually are the emotional ballast for them, providing not just the stability they need but the place for emotional expression that is unavailable elsewhere in most men's lives."

Rubin's contentions are based on her 15 years as a family therapist and interviews with 150 couples. Far more men than women, she has found, name their spouse as their best friend, or the one to whom they'd turn in trouble. And many more husbands than wives say they would remarry if they were widowed.

"He feeds on me," announced one wife matter-of-factly. "I don't know how much he understands it, but that's the real reason he needs me. I'm his tie to life, if you know what I mean."

An interview with a working couple was a comfortable one, until the subject of independence came up. According to the wife, a 35-year-old assistant to a personnel manager, the husband couldn't take a day off work unless she did, while she was perfectly happy alone, catching up on things, cooking, sewing, visiting friends.

"I sometimes think this big-man, powerful number they pull," said the wife, "is all just a cover for how dependent they are."

Instead of disagreeing, the husband, a 40-year-old financial consultant, tried to justify himself.

"What did I get married for if it's not to have someone to do things with and to share my life? If I have to hang around alone at night while she works or goes out with a friend, or spend vacations alone, why didn't I just stay single? Nothing's much fun without her, so why would I want to do it that way? She calls it dependency, but . . . I just say it's common sense. Most men feel just like I do."

Although Rubin takes the view that men are more dependent, the very structure of marriage, she says, protects a man from having to deal with his own dependency needs: "Women are the caretakers; they're not being taken care of except sometimes economically. They look very demanding at the emotional level, but I don't think that's true."

Men make more demands, she claims, but their demands aren't as overt as women's.

Part of the reason is the sort of Catch-22 built into our culture, that if a man shows his vulnerability, he may be considered a weakling.

"We women expect a man to be bigger, better, stronger, smarter than we. If he isn't--when we plead with him for his vulnerability and let him show that--we get nervous. Men know this; they are very careful about allowing dependency to show."

It is such "barriers to intimacy" Rubin believes we must acknowledge, along with the realization that men and women relate to each other differently in marriage. The current picture, she says, looks something like this:

"What she wants is the kind of connection where he can share his inner thoughts, and she wants him to want the same thing from her. She wants him to say to her, 'Tell me what's on your mind.'

"And what he wants from her is just the comfort of her presence. In some way, that enables him to relive that archaic past where he didn't need words--mother's presence was enough."

Those two disparate needs, she says, are often manifested in the couple's sexual relationship.

For example, one wife told Rubin, "I want to know what he's thinking--you know, what's going on inside him--before we jump into bed."

In contrast, the husband said, "To me, it feels like there's a nice bond when we're together--just reading the paper or watching the tube or something like that. Then when we go to bed, that's not enough for her."

Rubin, 59, who is married for a second time and has a grown daughter, has collected her interviews and insights as a family therapist in a new book called Intimate Strangers (Harper & Row, $14.95), geared primarily to men.

"Women know the issues," she says. "But no one has written for men in a way that made them understand that the ways in which they live their lives and ways in which the family is structured have been unhealthy psychologically for them."

Currently on the talk-show circuit ("Panorama," "Today," "Phil Donahue"), she has been encouraged by a positive response, even from men. She concedes, however, that the subject is not an easy one for them to address.

Evenings, while she was writing her book, she'd come down from her study to talk about it with her husband Hank, a wine columnist and managing editor of Vintage magazine. On the one hand, she says, he was pleased he wasn't like some of the emotionally distanced men she was writing about. On the other, he seemed threatened by the thought of being different--"that it was some statement about his own manliness."

Rubin doesn't offer any of what she calls "push-pull solutions" to bringing down the barriers to intimacy. Though self-help books often tell us, "You say this, he'll say this, and you'll live happily ever after," the results can be disappointing. It's not that simple.

But because of lengthening life expectancy and the fact that couples are likely to be married longer, she considers it more urgent than ever to understand the differences between men and women--why they exist and what they are.

Meanwhile,, she says, women need much less than they think they need, or that men think they need. Let a man come home and say after a disappointing sexual encounter the night before, "I was thinking this about our relationship . . ." and that's enough.

If he simply asks, "What's for dinner?" you've got a setup for another evening that will be strained or wind up in a fight.