My friend said it with a blush, but he said it, nevertheless: The reason the woman in question had succeeded so well was that she, blush, thinks like a man.

This was once a high compliment. Nowadays, in our age of enlightenment, it is merely sexist. But no one, of course, would dream of complimenting someone by saying he or she thinks like a woman. That would not only be sexist -- it would, in a lot of quarters, be taken as an insult. But why? Why is it wrong to think like a woman?

Carol Gilligan, an associate professor of education at the Harvard Graduate School of Education, believes that the answer lies in the history of psychological research, which has focused exclusively on the male pattern of thinking and has taken that as the norm against which all other thinking is measured. In her recently published book, "In a Different Voice," she argues that the "penchant of developmental theorists to project a masculine image. . . goes back at least to Freud (1905) who built his theory of psychosexual development around the experiences of the male child that culminate in the Oedipus complex."

In the 1920s, she writes, Freud sought to fit the female child into this developmental pattern and found he could not. That became a female developmental failure, from which Freud went on to conclude that women "show less sense of justice than men, that they are less ready to submit to the great exigencies of life, that they are more often influenced in their judgments by feelings of affection and hostility.

"Thus," writes Gilligan, "a problem in theory became cast as a problem in women's development, and the problem in women's development was located in their experience of relationships." And, she argues, the idea that women somehow have failed to develop has persisted ever since. The approved norm has been the independent, autonomous male who cherishes a rigid principle of impartial justice.Psychological theories and value systems have silenced the thinking of women and the concepts of morality that women bring to their decisions.

To argue her point, Gilligan uses literary situations, psychological studies of the way girls, boys, men and women evaluate a situation and her own study of how a group of pregnant women, all considering abortions, reached their decisions. Time and again in each of those illustrations, men emphasized abstract ideals of perfection, while women emphasized caring and responsibility to others. "The parameters of a clear moral perception emerged," she said in an interview. "The moral act was the act that didn't hurt anyone." Yet this voice that stresses the responsible act as being the caring act has been ignored in psychology, education, philosophy and society in general, she said.

While men are anchored in separation and concepts of rights, women are anchored in family relationships and interconnections. They are aware of different people's feelings, problems and choices, which sometimes makes their own choices more difficult. A male value system will justify a war over national honor; a female value system will say, "Wait, this soldier is someone's son," said Gilligan. A realization of this difference "raises a lot of questions about what kind of thinking is valuable as well as the values in our society," she said. "We've denigrated the caretaking activities."

And we have denigrated the way women think. "This has been described as an inadequate, undeveloped, naive voice, illogical," she said. "Rather than being called naive, aren't these values that can help address problems that affect both men and women?"

That women think differently than men and perceive problems and solutions differently is becoming strikingly apparent in public opinion polls. Poll after poll on the Reagan administration is finding that women are much more worried than men about the administration's impact on the poor and the disadvantaged and about its commitment to peace. Pollster Louis Harris found also that his polls were reflecting not only an emerging women's vote but a deep-seated desire by women to have their views and values recognized by society.

Gilligan's book explores the world of women's values and gives them legitimacy. "It's an unseen world and an unheard voice," she said, and her book is a first step toward representing it. It is by no means light reading, but to those of us searching for a better understanding of the way men and women think and the different values we bring to public problems and to our private lives, it is of enormous importance.