"When will we know when we can declare victory? For years I proceeded on the assumption that victory was equal participation of men and women in all branches of science and engineering. Today I’m not so sure.... It’s possible that we will come to understand that some fraction of the asymmetries in the distribution of women in the sciences, with women far more well represented in the life sciences and less so in the physical sciences, is the result of women seeking those fields in which they are able to make the greatest contribution in their own judgement. As scientists we have to be open to that possibility."
- Shirley Tilghman, President of Princeton University, speaking at Queen’s University 
The question of gender representation in science is an incredibly difficult one. Women are underrepresented in science as a whole, especially in senior positions, but the disparity can be even more dramatic, or in other cases disappear, when we narrow the focus to particular fields.
Over the last half-century, efforts to recruit and encourage women to pursue careers in science have been very successful, but they have not been evenly distributed. In 1966, for example, women earned only a quarter of the undergraduate biology degrees awarded in the U.S. By 2007, however, women out numbered men, taking 60 percent of these same degrees. In physics, though, these numbers have barely budged, with the percentage of undergraduate degrees earned by women rising from 14 percent to only 21 percent over the same time period. The question, of course, is why?
Most recent studies have shown very little difference in physics-related abilities between genders—not nearly enough to explain the large participation gaps. So what is keeping women out of physics? Is it, as Dr. Tilghman suggests, that women just don’t choose to put their efforts into physics because they feel they can make a greater contribution elsewhere? Or, maybe women are not interested because they don’t see how science fits with their desire to work with people, as was recently argued by Claire Cupples, the Dean of Science at Simon Fraser University.
These might seem like comforting explanations—no discrimination, no stereotyping, just choice—but they are also too simple.
What influences students’ decisions to pursue physics?
As early as the eighth grade, the interest that students show in science is one of the best ways to predict whether they will go on to receive a bachelor’s degree in science, a link which is even more important than their mathematics achievement at the same age.
Personal interest isn’t, however, the only factor. Students’ belief in their own abilities is extremely important. Students with high self-efficacy, confidence in their ability to succeed at particular tasks, tend to understand physics better and achieve better grades. This makes a lot of sense: if students don’t believe they have the ability to master new ideas and problems, it is easy to see why they might not persevere in trying to understanding difficult concepts. This relationship is true for both male and female students, but female students tend to believe in themselves less, contributing to the difficulties they can encounter in physics.
Parents, teachers and peers also have strong influences on students’ perceptions of their own abilities, affecting students' career and degree choices. In one study, students were followed from age 12 to age 24. Researchers asked the students and their parents about the student's math and science interests, abilities and career aspirations. They found that the more mothers believed in their children’s science and math abilities in grade 7, the more likely those students were to pursue careers in science at age 24. Peers can have a similar impact, supporting or eroding students’ belief in their own abilities. In another study, rural girls who were recognized as talented in science were strongly influenced by the recognition and support they received from their peers. These social influences can be troubling because parents, teachers and even peers often have stereotypical views of interest and ability in science, views that tend to favor male students.
Together, studies like these illustrate how challenging it is to pinpoint a single cause for the underrepresentation of women in physics. There are elements of interest and self-confidence, but also difficult social pressures. With these challenges in mind, what is needed is not acquiescence but continued searching for solutions. We still need to know what can be done to support and encourage students, and girls in particular, to pursue careers and graduate studies in physics.
Looking for solutions in high school physics experiences
One such effort, the Persistence Research in Science and Engineering Project  led by researchers at the Harvard-Smithsonian Center for Astrophysics, is trying to identify the impact of teaching environments and strategies on students’ decisions to enrol and continue in physics in university. As part of the project, they have surveyed 3,800 American undergraduate students about their physics interests, confidence and career plans, along with their experiences in high school physics classes.
From this survey data, my colleagues Zahra Hazari, Gerhard Sonnert, Philip Sadler and I created a measure of each student's "physics identity," the degree to which they perceive themselves to be the right type of person for physics. Being the right type of person means, for example, having confidence in their ability to complete the right tasks (for example, understand and solve difficult physics problems), having a strong interest in physics, having others recognize them as the right type of person, being successful in physics, and choosing to participate in physics-related activities. We found that our measure of identity was a very good way to predict students' desire to remain in physics and pursue it as a career.
Once we were confident that our measure of physics identity was a valid way of bringing together many of the social and personal factors that tend to influence career choice, we wanted to know what could be done to improve it. As a former high school physics teacher, I was particularly interested in finding out which teaching strategies or classroom activities can contribute to stronger and more positive physics identities, especially for female students.
To answer these questions, the PRiSE questionnaire asked students what they remembered about their high school physics experiences: what they did in class, how they were taught, and the types of resources they had available. In addition to strictly pedagogical questions about lab time versus lecture time, topics that were emphasized, and instructional strategies that their teachers used, we were also interested in whether students recalled their teachers taking time to address subjects that generally fall outside of the usual physics concepts such as discussions of the benefits of and steps needed to pursue a career in physics, ethical considerations in science, and the under-representation of women.
Supporting women by recognizing underrepresentation
Looking at all of the students, male and female, there were several classroom factors that were related to stronger identities. From the perspective of student interest, it wasn’t surprising that teachers who introduced current and cutting-edge physics topics contributed to stronger identities. Frequent labs addressing students’ beliefs about the world, opportunities for peer teaching, and encouraging student questions were also related to stronger physics identities. Students with stronger identities also remembered receiving encouragement from their teachers to pursue physics and having discussions in class about the benefits of being a scientist.
But what about women in particular?
Usually, the strategies that come to mind for encouraging female students include providing positive female science role models, creating opportunities for collaborative group work, and discussing the lives of female scientists. We were very surprised, though, that none of these usual solutions had an effect on the physics identities of the students in our study. Female students who experienced them were no more likely than others to have strong or weak identities in physics.
There was only one classroom experience that had a uniquely strong impact on female students: the explicit discussion of underrepresentation of women in science. This isn’t just highlighting women scientists like Marie Curie but instead talking directly about the fact that there are few women in physics. Female students who had experienced these discussions in their high school classes had significantly stronger physics identities. And further, these discussions had no impact on male students. In other words, for students who experienced explicit discussion of female underrepresentation in physics, the potential physics career gap was decreased.
While addressing her audience at Queen's, Dr. Tilghman suggested we might reach a point where there are as many women in some areas of science as want to be there, with any remaining gender gaps the result of choices made by women themselves. Our analysis shows that we are not there yet; social influences are still very important for determining if students will pursue a career in physics. Student's opinions are far from fixed, and good science teachers can have an important effect on their students' physics identities. Most importantly, teachers who did something as simple as acknowledging the gender imbalance in physics could be enough to help encourage female students toward a physics career.
 Her talk was broadcast as part of an episode of the CBC Radio program Ideas.
 Hyde, J.S., & Linn, M.C. (2006). Gender similarities in mathematics and science. Science, 314, 599–600. [doi: 10.1126/science.1132154]
 Tai, R.H., Liu, C.Q., Maltese, A.V., & Fan, X. (2006). Planning early for careers in science. Science, 312, 1143–1144. [doi: 10.1126/science.1128690]
 Cavallo, A.M.L., Potter, W.H., & Rozman, M. (2004). Gender differences in learning constructs, shifts in learning constructs, and their relationship to course achievement in a structured inquiry, yearlong college physics course for life science majors. School Science & Mathematics, 104, 288–300.
 Bleeker, M.M., & Jacobs, J.E. (2004). Achievement in math and science: Do mothers’ beliefs matter 12 years later? Journal of Educational Psychology, 96(1), 97–109.
 Jacobs, J.E., Finken, L.L., Griffin, N.L., & Wright, J.D. (1998). The career plans of science-talented rural adolescent girls. American Educational Research Journal, 35, 681–704.
 Kessels, U. (2005). Fitting into the stereotype: How gender-stereotyped perceptions of prototypic peers relate to liking for school subjects. European Journal of Psychology of Education, 20, 309–323. [doi: 10.1007/BF03173559]
 Funded by the National Science Foundation (NSF), PRiSE surveyed a nationally representative sample of college/university students enrolled in introductory English courses in the fall of 2007 about their interests and experiences in science. The survey can be viewed online at www.cfa.harvard.edu/sed/projects/PRiSE_survey_proof.pdf
 This post is based on findings published in our paper: Hazari, Z., Sadler, P. M., Sonnert, G., & Shanahan, M.-C. (2010). Connecting high school physics experiences, outcome expectations, physics identity, and physics career choice: A gender study. Journal of Research in Science Teaching, 47, 978–1003. [doi: 10.1002/tea.20363]
About the author: Marie-Claire Shanahan is an assistant professor of science education at the University of Alberta in Edmonton, where she studies the interactions that people have with each other in science—in classrooms, meeting rooms and online. She is President of the Canadian Science Education Research Group and a member of the Centre for Mathematics, Science and Technology Education. She blogs at Boundary Vision and tweets at @mcshanahan. When she isn't teaching, visiting research sites or writing, she can be found exploring the Edmonton river valley with her dogs, who, despite her best efforts, have not yet developed the ability to ask scientific questions.
The views expressed are those of the author and are not necessarily those of Scientific American.