More than 35 years after the first women graduated from Yale College, females now represent half of every entering class. But men and women are not equally represented everywhere on campus, just as administrators predicted in 1969.

Elga Wasserman, who coordinated planning for the arrival of women on campus, told the 1969 Yale Banner that the University would probably have to expand courses in English, foreign language, psychology and art “to accommodate female interests.”

Data on enrollment in Yale College majors — broken down by sex and provided to the News by the Office of Institutional Research — show that in 37 years of coeducation, women continue to be overrepresented in the fields that Wasserman identified in 1969. In both 1978 and 2005, engineering, physics and mathematics lagged behind many of the humanities departments in attracting women, who tend to flock to fields ranging from art history to English, as well as the “softer” sciences, such as biology and environmental studies.

Administrators and professors said they are aware that men and women are not spread equally through different departments, and Yale funds programs to encourage women to participate in the sciences. At the same time, some professors speculate that men and women are not equally interested in math and science, so efforts to achieve parity across the curriculum may be futile.

But the choice not to major in science also has broader repercussions for society, as current research shows that jobs that require ability in mathematics garner significantly higher wages than other positions. Six years after Yale President Richard Levin committed $1 billion to the sciences at Yale, it may be time to revisit the reasons why female students seem to shy away from the physical sciences ­– while embracing biology — and their male peers are less likely to major in the humanities and interdisciplinary fields. Research on student choices in majors is not conclusive, but professors both outside of and within the University have proposed a range of explanations for the disparities, from discrimination to inherently different interests.

Three decades of a ‘gender gap’

In the 2005-’06 school year, anthropology, environmental studies, art history and psychology are among the majors in which women are most overrepresented. At the same time, women are underrepresented in many of the physical sciences, including electrical, chemical and mechanical engineering, mathematics and physics.

Women make up 42 percent of all science majors, but only 32 percent of science majors other than biology and molecular biophysics and biochemistry. They are also underrepresented in several mathematics-heavy social science disciplines, such as economics, where 26 percent of majors are women.

In contrast to the sciences, women make up 62 percent of majors identified as “other” in University data, which include interdisciplinary programs such as East Asian studies, as well as art and architecture, which are connected to the professional schools. There are only four science-related majors in the “other” category: cognitive science, environmental studies, applied mathematics and history of science, history of medicine. Of those four, women comprise a majority of students in all but applied mathematics.

The interdisciplinary nature of these science majors attracts many women who might otherwise have chosen a departmental science major. For environmental studies major Caitlin Clarke ’07, the program is a good way to combine her interest in the humanities and the sciences. It is applicable to the real world, she said, and she plans to pursue a career in environmental law, in government or at a nongovernmental organization.

“Environmental studies turned out to be a way that I could use political science and philosophy and straight science and sociology,” she said. “It really allowed me to combine all of my interests.”

The differences between men and women’s choices in majors are less exaggerated when viewed in terms of department popularity instead of sex representation. Sixty percent of men and 50 percent of women are enrolled in the same six majors: history, political science, English, psychology, biology and economics.

But the durability of the “gender gap” over time is striking, particularly in mathematics and the physical sciences. Compared to the ratio in 1978 — when women comprised 37 percent of the student body — the proportion of female to male students has changed little in engineering, physics and mathematics. Women were 29 percent of engineering majors in 1978, and they are 30 percent today — but now they make up about 50 percent of the student body. The percentage of female physics majors was 24 percent in 1978; it is 26 percent now.

Physics Department Chair Ramamurti Shankar said he was surprised that the 1978 ratio of women to men in the physics major was so high. The fraction of women declined with the overall number of physics majors during the 1980s and 1990s, Shankar said, and the department has recently been working to increase overall enrollment, as well as the representation of women.

“What this means is we’ve just gotten back to where we were,” Shankar said.

Of the sciences, chemistry has seen the largest increase in female enrollment since the late 1970s. Female enrollment in the major was 18 percent in 1978, and women now make up 50 percent of undergraduates in the department. The Chemistry Department has recognized the growth in female enrollment in the major and graduate program, Director of Undergraduate Studies John Wood said.

“We can’t really help but notice it, and it’s great,” Wood said. “But exactly why that’s the case, I don’t have a good explanation for it.”

The biology major has also seen an increase — it is now 56 percent female, compared to 42 percent in 1978.

Several professors and researchers said they are disappointed by the relatively unchanged low level of females majoring in mathematics and the physical sciences. Physics professor Meg Urry, the first woman to receive tenure in Yale’s physics department and an advocate for women in science, said she would have expected physical science programs to follow the precedent set by medical schools. The first generation of women to enroll in medical schools faced hostile environments, she said, but the transition to equal enrollments happened fairly rapidly. Physics programs nationally, on the other hand, did not see the same growth in female enrollments after the first women were admitted, she said.

But it is not too late for enrollment ratios to change in the physical sciences.

Astronomy professor Charles Bailyn said astronomy — both nationally and at Yale — has seen a sudden growth in the enrollment of women both on the undergraduate and graduate levels. Astronomy is in the midst of a “tipping point” similar to that which occurred in biology several years ago, Bailyn said, when the percentage of women majors increased very quickly after a period of relatively constant enrollments.

“You get to a point where if there’s a critical mass … it becomes a kind of friendlier and more inviting atmosphere,” he said.

Improving girls’ access to math and science classes has long been a focus of elementary- and secondary-school educators. Catherine Weinberger — a researcher at the University of California, Santa Barbara whose research focuses on gender gaps in wages and academics — said male and female participation in science classes in high schools is approaching equal levels, especially among the highest-performing students who see science as a critical part of a college-prep curriculum.

But this preparation does not seem to translate to parity in undergraduate science major enrollments at Yale and at other universities across the country.

“It’s really a mystery why this one area has been so different and so much harder to change,” Weinberger said.

The representation of women was calculated by comparing the percentage of women in each major with the percentage of women in the junior and senior classes in 1978 and 2005, respectively. The use of two-year averages controlled for expected variation between class years, while majors with fewer than 10 students were excluded from the sample.

Intrinsic aptitude, diverging interests or cultural pressures?

Professors grope for an explanation for the continuing “gender gap” among undergraduates, while avoiding the trap represented by outgoing Harvard President Lawrence Summers and his statements about “intrinsic aptitude.”

At a conference last year, Summers suggested that women may be underrepresented in the sciences because of innately lower abilities. He was promptly vilified by female scientists nationwide and censured by the Harvard faculty, and the incident is widely thought to have contributed to his resignation in March of this year.

But some Yale faculty members hinted that there may be intrinsic differences in interests, if not in aptitude, that lead more men than women to major in the “hard” sciences. Norma Thompson, the director of undergraduate studies for humanities, said it is not accidental that patterns of enrollment over time have remained relatively fixed.

“It just seems to me to be undeniable … in terms of the specifics of knowledge and the preponderance of interest, that we do have some difference here,” Thompson said.

Other professors suggested that women’s apparent lack of interest may be due more to cultural norms than a genuine distaste for the sciences. Mathematics and the physical sciences are still perceived as “male domains,” which are potentially hostile environments for women, said Marianne LaFrance, director of undergraduate studies for psychology.

“It’s not necessarily that women assume that they’re going to be harassed,” LaFrance said. “They still think … if I always have to confront this, why don’t I go someplace where I will not have to fight that battle?”

Hunter College psychology professor Virginia Valian, who studies gender equity in academia, described the “schema” for a scientist’s personality as independent and good at “getting down to the business at hand.” This characterization seems to better fit the stereotype of a male personality, whereas women are supposed to be more nurturing and communal, she said. Since most people internalize such schemas to some degree, Valian said, science seems to be an inappropriate career choice for women.

“We start picking those things up very early at life,” Valian said. “The people who are helping us decide what we want to be also have those views in a very full-fledged way, and without intending to, they communicate them.”

The careers that seem to follow naturally from a degree in math and science may also seem less appealing to women, researchers said.

Jane Margolis, an education researcher at the University of California, Los Angeles who focuses on women in computer science, said the cultural norms of computer science — the image of the programmer “hacking for hacking’s sake” — is less appealing to many women because it does not appear to be connected to the broader world.

In surveys, Weinberger said, college-age women say they want to pursue a career that will allow them to help society or other individuals.

“They may not understand how much you can do that with technical skills,” Weinberger said.

Curricular changes emphasizing the applications of computer technology, ranging from biology to architecture to medicine, may help retain women beyond the introductory level, Margolis said.

University intervention

Among professors who believe cultural barriers deter women from entering the sciences, there is a belief that the University has an obligation to break down these barriers by improving faculty diversity and supporting women with interests in science. But other professors said the lack of gender balance across different majors is not necessarily problematic if it reflects students’ genuine preferences for one field or another.

Yale President Richard Levin said the issue of underrepresentation in the sciences “merits attention,” both at Yale and peer institutions. At Yale, the STARS program — Science, Technology and Research Scholars — attempts to engage women and underrepresented minorities in scientific research early in their college careers. STARS participants receive research stipends and additional mentoring to encourage them to major in natural science and engineering fields.

Margolis said the presence of women in technical fields such as engineering and computer science is important for individuals because of the vast opportunities existing for workers with such expertise. More broadly, society benefits when technology is designed by a diverse team that is aware of the needs and preferences of a wide swath of society.

“It affects us all by not having diverse perspectives at the design table,” she said.

The jobs available to those with degrees in math and science are often better paid than positions available to graduates with comparable degrees in the humanities. Much of Weinberger’s research has concentrated on the link between the gender gap in wages and the gender gap in college majors, and she said up to one half of the national wage gap can be explained by undergraduate major choice. Engineering and computer science majors typically earn 30 to 50 percent more than their peers in any other fields, she said.

While students are still in college, underrepresentation of men or women can affect both the classroom environment and the quality of discussion, professors and students said.

In the humanities, where men are 32 percent of junior and senior majors this year, Thompson said she thinks an imbalance of men and women can seriously affect classroom dynamics. Thompson said that in humanities classes, where discussions often touch on the relations between the sexes, it seems wrong to have only the female viewpoint represented.

“I don’t think most people are comfortable in situations where there is such an imbalance,” she said. “It’s just not true to life.”

Applied mathematics major Erica Newland ’08 said she thinks male students tend to speak up more forcefully in class than women, which may be exacerbated if there are few women in the course.

“Most of the guys really don’t care about being wrong,” said Quentin Lindsey ’07, a mechanical and electrical engineering major. “We’re really not worried about the consequences. The women in my classes usually aren’t asking as much.”

In classes with more women, students said, anxiety about being correct or appearing aggressive seems to be lessened. Clarke said that in her classes, the large fraction of women seems to encourage more women to speak up in discussions.

But several professors, including Thompson, suggested that even representation is not a realistic goal in all disciplines if levels of interest continue to differ. History professor Cynthia Russett, who studies 20th century women’s history, said administrators should focus on ascertaining whether men and women have equal opportunities to enter different majors, but equalizing participation may be an impossible task.

“The student body may be very gendered, but I haven’t heard students complaining about this,” said Helen Siu, the director of undergraduate studies for anthropology, where women are 86 percent of junior and senior majors this year.

Some students said while equality is desirable, the University should be wary of pushing students toward one discipline or another.

“In a perfect world, it would be fantastic for [majors] to have even numbers,” said anthropology major Paul Morse ’08. “But I would like to think the majors don’t have to recruit anyone. I would rather that people just make that decision on their own.”

‘Pioneers tromping through snowdrifts’

So far, attempts to achieve a more even distribution of men and women in different undergraduate majors have focused on making the environment in different departments more comfortable for female students.

Faculty and administrators point to the availability of same-sex mentors as a possible factor leading more women to major in certain fields. Russett said it may be difficult for women to imagine a career in a field where all of the leaders are men.

“If you just don’t see people out there who can be role models, it’s not in the horizon of possibility,” she said.

Ruth Toner ’07, a physics major, said she found a mentor early in her Yale career when she worked in Urry’s lab after her freshman year. Although Toner now works in a lab that is almost entirely male, Urry’s advice and support was particularly helpful as a freshman, she said.

“If there are women, it encourages more women to join,” Toner said. “It’s a mentoring thing.”

Last fall, the University pledged to hire 30 new female professors over the next seven years. Currently, women make up about one quarter of the ladder-track faculty across all departments, but only 10 percent of all professors in the physical sciences division are female.

The representation of undergraduate women in a given field appears to increase with the presence of female faculty in the relevant department. But the correlation between the two variables explains only about a quarter of the sex-ratio differences between majors, suggesting that factors other than mentoring are at work.

Weinberger said research on the impact of mentoring has had mixed results. The presence of female faculty alone will not lead more women to major in a field, Weinberger said, but it is important that women feel welcome in the major.

“You definitely want to make sure that the women who choose to become scientists and engineers are valued and can do that without always having to feel like they are pioneers tromping through snowdrifts,” she said.

Urry said one step to attracting more women into the “hard” sciences is to revise the curriculum so it is more inviting to students who may not be initially interested in a given discipline. In her introductory course, “Advanced General Physics,” Urry eliminated curves from grading and added more cooperative, small-group activities. Urry said she thinks the changes may have made the course more appealing to women by increasing opportunities for collaboration rather than emphasizing competitiveness.

But curriculum revisions require a significant amount of labor on the part of the instructor, she said, so even excellent teachers may be reluctant to overhaul the strategies that have worked well in previous years.

“For a lot of people, there’s just a huge activation energy barrier to doing this,” she said.

Shankar said professors throughout the Physics Department have worked hard to increase the number of women studying the sciences. Faculty members teaching introductory courses work to retain women who would otherwise “drop out for the wrong reasons,” Shankar said, and the department has placed an emphasis on hiring female professors. Today there are three female professors teaching physics at Yale.

Students said they have begun to notice a change in the gender balance in the major. Data is not available for freshman and sophomore physics majors, since they have not officially declared their plans, but Toner said she has seen more women in introductory classes.

“My year for physics is almost entirely male, but the sophomore intensive major has a much better gender balance,” she said.

Awareness of the undergraduate sex ratio has grown enormously since 1978, Shankar said, even if the proportion of women has not grown substantially.

“Back in the day, people didn’t think about it,” Shankar said.

Today, Shankar said, the department “thinks about nothing else.”

In his own introductory class, “Fundamentals of Physics,” the top students are men and women in roughly even proportions, Shankar said. But he still sees comparatively few of the women go on to major in the discipline.

“We should not be satisfied with these numbers, because this is not the ratio of strong women in my class,” Shankar said.