Study after study finds that many women feel unwelcome in laboratories and science departments, even after considerable progress in encouraging women to study science and technology fields.
As these studies come out, there are almost always skeptics who say that whatever gender imbalance exists could well reflect different choices made, on average, by men and women, or who say that individual men are rising on their merits, not sexism.
But a new study in Proceedings of the National Academy of Sciences offers evidence of bias among scientists - male and female scientists alike - against female students.
The study was based on evaluations by scientists of hypothetical student applications for a lab manager position, with the application materials identical in every way, except that half of the pool received applications with a male name and the other half received applications with a female name.
The faculty members surveyed - 1 professors in biology, chemistry or physics - were told that their analyses of the applications would be used to help the students. And they were asked to evaluate the students' competence and "hireability" and to consider how large a salary they would recommend and how much mentoring they would offer the student if hired.
The scientists evaluating these applications (which were identical in every way except the gender of the "submitter") rated the male student more competent, more likely to be hired, deserving of a better salary, and worth spending more time mentoring. The gaps were significant.
Female scientists were as likely as male scientists to evaluate the students this way. For instance, the scientists were asked to rate the students' competence on a 5-point scale. Male faculty rated the male student 4.01 and the female student 3.33. Female scientists rated the male student 4.10 and the female student 3.32.
On salary, the gaps were also notable. The average salary suggested by male scientists for the male student was $30,520 (£18,831); for the female student, it was $,111. Female scientists recommended, on average, a salary of $29,333 for the male student and $25,000 for the female student.
The authors - Corinne A. Moss-Racusin, John F. Dovidio, Victoria L. Brescoll, Mark J. Graham and Jo Handelsman - are an interdisciplinary team at Yale University representing biological and social sciences.
They write that the differences they found were statistically significant, and "suggest that subtle gender bias is important to address because it could translate into large real-world disadvantages in the judgment and treatment of female science students".
On the issue of female scientists and male scientists making similarly apparently biased judgments, the authors had this to say: "It is noteworthy that female faculty members were just as likely as their male colleagues to favor the male student. The fact that faculty members' bias was independent of their gender, scientific discipline, age and tenure status suggests that it is likely unintentional, generated from widespread cultural stereotypes rather than a conscious effort to harm women."
Adding to the authors' view that their findings show bias: the faculty members reported "liking" the female student more than the male student, but ranked the male student higher on professional matters.
Of particular concern to the authors was the potential impact of such bias on students as they are deciding on their careers and whether to pursue advanced degrees in science. The hypothetical student (male and female versions) was described to the faculty members with the kind of characteristics (such as having co-authored a study after two years of research experience) that should identify students as having real potential in science. "Our results raise the possibility that not only do such women encounter biased judgments of their competence and hireability, but also receive less faculty encouragement and faculty rewards than identical male counterparts."