U.S. graduate students in the agricultural sciences are more likely than those in other fields to carry out interdisciplinary research, according to a first-ever analysis  of the issue by the National Science Foundation. And the Massachusetts Institute of Technology leads the nation in the percentage of its doctoral students whose dissertations involve more than one discipline. But beyond that, it's not clear what the data say about this important subject.
It's an article of faith among science policymakers that interdisciplinary research is essential to address society's most pressing technological challenges, from energy independence to improved health care. But don't ask them to measure it. The National Academies' upcoming assessment of doctoral research programs, for example, asked departments what percentage of their faculty members were associated with other programs. But the data "aren't very satisfactory," says Charlotte Kuh, study director. Part of the problem is the fuzzy definition of an interdisciplinary program, she adds.
In 2001 NSF began asking newly minted doctoral students if their dissertations spanned more than one field, and in 2004 added an explicit reference to interdisciplinary research. This week its Division of Science Resources Statistics issued the first analysis of those responses, through 2008, to its annual Survey of Earned Doctorates.
NSF found that the extent of interdisciplinary dissertation research overall has been steady throughout the decade at around 28%. Graduate students in the agricultural sciences top the list, with 39% of them declaring a second field. Those in the biological and geosciences were next, at 35%. At the bottom are graduate students in the computer sciences, mathematics, and psychology, with only about 20% going outside their primary discipline for their dissertation.
MIT leads the pack of institutions, with 44% of its doctoral students reporting more than one dissertation field. (Of the 44,000 respondents to the 2008 survey, fewer than 2% listed more than two fields.) Seven other institutions topped 35%.
NSF officials say the survey doesn't address the larger question of how difficult or easy it is for students to pursue interdisciplinary degrees, nor the extent to which senior faculty engage in interdisciplinary research themselves. An ongoing NSF survey of academic research piloted a question about how much is being spent on such activities, and where on campus the research takes place. But that proved to be a tough question for research administrators to answer, says one program manager, and the results may not be usable.