Social pressures, not biology, are responsible for the fact that boys traditionally do better in mathematics than girls, according to David Maines, author of a new study on math and sex.

The study, a two-year investigation of the life histories of 168 male and female college mathematics majors, is the latest volley in a continuing academic battle over the extent to which boys and girls differ naturally and the extent to which they become different at the hands of society.

Maines said his study for the National Institute of Education counters the conclusions of a 1980 study of 10,000 children done at Johns Hopkins University, which found that boys on the average score higher on mathematical reasoning tests and suggested that genetic factors should not be discounted as an explanation for the difference in performance.

Maines said his study demonstrates the powerful effect of social factors in the way males and females approach the subject of mathematics, and concluded that their performances differ for social reasons rather than biological ones.

Julian Stanley, co-author with Camilla Benbow of the Johns Hopkins study, said neither study addressed the question of genetics at all; Maines agreed, but said his study does show the strong social nature of girls' approach to the study of mathematics.

Both researchers pointed out that the difference between boys and girls is only statistical, and in the real world the abilities are closely similar, and any given girl may be much better at math than any boy.

Maines said that the chief difference between male and female math majors was that the females were not as interested in mathematics for its own sake, and were not willing to let the subject completely dominate their lives as the males were.

Some of the conclusions of the study:

* About 67 percent of the women said that they received strong encouragement to go into mathematics, but only 40 percent of the men said they were encouraged.

* Some women received confusing signals about majoring in mathematics; 41 percent said they were discouraged from going into math, while only 20 percent of the men said they were discouraged.

* When asked the biggest problems with being a math student, 64 percent of the men named mathematical problems, but only four percent of the women did so. Instead, 65 percent of the women named social factors, such as relations with others, as the biggest problems.

* The female students worked far fewer hours at their studies, with 71 percent of the males studying six hours or more per day, and only 28 percent of the women studying that long.

* Females have more "role models" -- people they admire and want to emulate -- than the males, but these tend to be friends or family rather than academic figures; more of the male role models were math professors.

* The women "had very negative feelings about their female math professors, a far more negative attitude toward the female professors than the males had," Maines reported.

* More of the men, 64 to 41 percent, went into mathematics because of their interest in the subject. Most of the women majored in math for other, social reasons such as wanting to be with people in the program or to adjust college schedules to fit better.

Maines said a theme that emerged from the whole study is that the men in mathematics "go ahead in math almost regardless, independent of encouragement or discouragement.

"That's the theme: the assertion that females are much more sensitive to social relations, pressures and norms.

"Males somehow are implicitly permitted, if pursuing an occupational thing of some sort, to ignore social matters and social etiquette," Maines said.

He said a result is a certain "diffuseness" in the women's attitude toward math. "This is dysfunctional for females who are trying to pursue something that is as demanding and takes as much focus and dedication."

Maines said he found women just as capable as men in mathematical pursuits, but said they were more often the targets of anti-mathematical pressure from parents, teachers and friends who encourage boys toward single-minded concentration on mathematics. Maines said those same authority figures place pressure on girls to have "diverse interests, including family obligations."