The United States is experiencing a groundswell of change in its perception of the single life. The social stigma of remaining single is diminishing as more young adults postpone or forgo marriage to continue education or pursue a career.
According to a study recently released by University of Michigan researchers Arland Thornton and Deborah Freedman, the ''legitimacy of singleness as a life style is increasingly recognized by young people and their parents.'' This acceptance of single life as a valid alternative to marriage represents a ''marked attitudinal shift'' in the US over the past two decades, the researchers report, with similar trends observed in western and northern Europe, Canada, and Australia.
''Women who never wanted to be wives or have children have the option now. Men are able to marry later and not make a forced early marriage just to maintain status in society,'' says J.L. Barkas, author of ''Singles in America'' (New York: Atheneum).
''There is still a trace of the feeling a woman hasn't been asked or a man hasn't found the 'right one,' but that is changing,'' she says.
According to US Census Bureau figures, slightly over 25 percent of all American households are composed of persons living alone or with non-relatives. The total number of single adults, defined as those not living with a legal spouse, has risen 26 percent since 1971 - from 43.8 million in 1971 to 55.8 million in 1979.
These numbers reflect, in part, the growing numbers of divorced people who prolong the time between marriages or do not remarry at all; widows and widowers (the largest group); those following what one sociologist calls ''the fallacious doctrine of open marriage;'' and young adults postponing marriage. The singles image
Following the high-water mark of family solidarity in the 1950s, media hype exalted the single life style in the '60s and '70s touting fewer responsibilities, sexual freedom, and more spendable income.
''The hoopla of the overly positive press has done as much to hurt singles as the negative image. The single is not the depressive or the swinger. Both (images) decrease the chance of seeing singles for themselves,'' says Miss Barkas.
Despite the media image of glorified singleness, David Reisman, professor of social sciences at Harvard University, sees a ''return to the belief that being single is not all that glamorous.''
Young Americans may be postponing a marriage decision, but according to the Thornton-Freedman study, they are not rejecting marriage as an institution, and 90 percent expect to marry at some time in their lives. The major change, the researchers say, is the rising age at which they will marry. Postponing marriage
Dr. Reisman believes the prevalence of divorce affects the way young people look at marriage. ''Children of divorced parents may be concerned about the stability of marriage and hesitant to make a commitment,'' he says.
The tendency to postpone marriage in favor of establishing a career or further education figures prominently in the decisions of many young people today. According to the Thornton-Freedman report, which was based on an 18-year study of Detroit families and several national studies, education was given a high priority over getting married right away by all respondents. Eighty to 90 percent of all respondents said they believed that it was very or somewhat important to work full time for a year or two before getting married. Fewer than 4 percent rated it as not important at all. Effect of the women's movement
The affluence and independence of young working women today has affected the marriage rates. In her book ''Single in America,'' J. L. Barkas writes that it used to be only men who wanted to establish themselves in careers, achieve a good income, and travel before settling down. Now more women are opting for a ''life before marriage,'' and fewer are willing to put husbands through college or graduate school by taking low-level jobs. Unfortunately, she says, some career-oriented singles (both male and female) find they are paying the price of a life that has overemphasized work.
''There is a great tragedy here,'' says Professor Reisman. ''Women do not realize the inequity of gender. Men can generally marry at any age, but for a woman the chance of marriage after 40 is not great. The result is a number of women who have waited too long.''
He says some women ''who have worked so hard for careers'' find work is not ultimately rewarding. ''Women have denied in themselves their maternal wishes. By the time it is too late to have children, they are regretful.''
Miss Barkas says the single years of a woman in her 30s often take on a very different character than those of a single man. A single woman in her 30s wanting to have children is concerned she might be cutting off the opportunity to have a family of her own, whereas men can postpone the responsibilities of marriage since ''there is nothing he has to worry about missing.''
Her most recent research, however, has revealed more women who do not feel they have ''missed the boat'' or even have the ambition to succeed financially, but have made the conscious decision they do not want to be wives.
''There is more of a feeling of control - 'This is what I choose, this is what I want,' '' she says.
Sociologist John Mogey of Annapolis, Md., believes the tendency to postpone marriage is due, in part, to heightened expectations regarding marriage.
''I think people are wanting more from close and intimate relationships. There has been a major change in the attitude of women and what they expect from life in terms of equality, respect, and personal satisfaction. Some are choosing to remain single rather than accommodate their wishes to men.''
Conversely, Dr. John Reisman says, (College-educated) men may be reluctant to enter into a long-term relationship because they fear they won't be able to ''live up to'' the new expectations of marriage, such as sharing child-rearing responsibilities and taking on the demands of a two-career marriage.
Many singles find that once they are out working it becomes more difficult to find and associate with peers. A 25-year-old single woman in Boston says, ''It's harder to meet people the longer you are out (of school) unless you really make an effort. Also, the longer you are single, the more you get used to doing things your own way.''
To help meet the needs of singles, more enlightened forms of the traditional singles clubs are emerging with the emphasis on hobbies or special interests rather than on seeking a mate. In the San Francisco Bay area, for example, singles can join the Intelligent Singles in San Rafael (qualifications permitting) or can discuss classics once a month with the Oldest Established Permanent Floating Book Club in San Francisco. In New York City there are cultural clubs where singles meet to attend a play or ballet. The long-range impact
What the trend toward prolonged singleness means for society in the long run is subject to debate. Some see it as the unraveling of the fabric of society - the demise of family life. Others see the trend as the basis for more stable and meaningful marriages.
In the long-range scenario, sociologist John Mogey predicts that households will remain smaller and individuals will tend to move more often. He sees the social acceptance of the single life as an opportunity for realizing a greater variety of objectives and achievements in a person's lifetime. ''If the choices are there to marry or remain single and the choice is made freely, it's a good thing,'' he says.
Dr. John Reisman sees potential demographic and educational shifts resulting from the trend toward prolonged singleness. ''When educated people are not becoming parents, children are going to come from the most impoverished elements of society,'' he says.
But because later marriages are often based on more mature decisions and a sounder economic basis, Dr. Reisman asserts, ''The marriages that do occur and sustain themselves, including second marriages, will be stronger than ever.''
In any case, life will be somewhat easier for those who remain single, say researchers Arland Thornton and Deborah Freedman: ''Those who do not marry, either because of active choice or because things just work out that way, probably will be the object of fewer negative social sanctions, and failure to marry will less often be viewed as a personal catastrophe.''