Japan strong in basic science and specialization, but weak in multidisciplinary collaboration — Survey of top 10% papers from 12 countries and regions in Asia, Europe, and America

Interdisciplinary research, which involves collaboration across multiple fields, demonstrates significant effectiveness in improving productivity, promoting innovation, and addressing complex problems. However, Japan's efforts in this area fall short compared with other countries. A survey conducted by The Science News and Elsevier examined the top 10% of papers in terms of interdisciplinarity from 12 countries and regions in Asia, Europe, and America, and revealed that Japan has the lowest proportion of interdisciplinary research, with disciplinary diversity of contributing authors (DDA) at 7.7% and disciplinary diversity of cited references (DDR) at 8.5%. In contrast, Europe and America showed high proportions exceeding 10%, while in Asia, Taiwan stood out, surpassing Singapore. Strategic policy initiatives are needed to improve this situation.

DDA is an indicator that measures the extent to which authors from different fields collaborate on research projects. The authors' specializations are determined based on the subject areas reflected in Scopus author profiles. This value reflects the diverse disciplinary backgrounds of a paper's co-authors. To measure it quantitatively, the calculation takes into account the number of different fields represented among co-authors (for example, if a paper's co-authors come from biology and chemistry), the cognitive distance between these fields (calculated from co-citation relationships; for instance, biology and chemistry have a smaller cognitive distance than biology and astronomy), and the balance among these fields. DDR is calculated using the same method as DDA but measures the diversity of cited papers. The analysis covered papers published from 2010 to 2024.

Interdisciplinary research is particularly effective when addressing complex, multifaceted problems that span multiple domains, such as health, environmental issues, and socioeconomic challenges. This is because interdisciplinary teams enable multifaceted approaches and can develop more comprehensive and effective solutions.

Prior research in Europe and America has revealed an increasing tendency for scientific breakthroughs to emerge from collaborative research by interdisciplinary teams. It has been found that papers with high DDA are strongly associated with academic impact (citation counts), while papers with high DDR are strongly associated with social impact (usage rates).

The DDA rankings for the 12 countries, starting from the highest, were: the Netherlands 12.3%, Switzerland 12.2%, the United Kingdom 12%, Taiwan 11.9%, France 11.5%, Singapore 11.4%, the United States 11.2%, Germany 10.6%, India 10.5%, South Korea 9.2%, China 8.3%, and Japan 7.7%, revealing that Japan has the lowest diversity among co-authors.

The DDR rankings were: the United Kingdom 11.2%, the Netherlands 10.8%, the United States 10.7%, Switzerland 10%, Germany 9.8%, France 9.8%, Taiwan 9.6%, Singapore 9.1%, China 8.9%, South Korea 8.9%, India 8.7%, and Japan 8.5%. While Asia is relatively lower than Europe and America, Taiwan demonstrates high interdisciplinarity, surpassing Singapore.

Even when examining papers by field, Japan's percentages remain low. In the medical field, DDA is 6.5% and DDR is 6.9%; even in materials science, one of Japan's strengths, DDA is 7.1% and DDR is 8%.

Then, outcomes were analyzed for the United Nations SDGs (Sustainable Development Goals)—Goals 3, 5, 7, 9, and 13. While DDA and DDR tended to be low for SDG 3 (Good Health and Well-being) and SDG 7 (Affordable and Clean Energy), Japan's DDA and DDR both exceeded the average of all countries for SDG 5 (Gender Equality), SDG 9 (Industry, Innovation and Infrastructure), and SDG 13 (Climate Action).

SDG 5 is led by the University of Tokyo, Kyoto University, Shionogi & Co., Ltd., the University of Osaka, and Hiroshima University, with keywords including COVID-19, intimate partner violence, gender inequality, domestic violence, sex differences, and HIV. SDG 13 is centered on the University of Tokyo, Kyoto University, the National Institute for Environmental Studies, Kyushu University, and Hokkaido University, with the main keywords of carbon dioxide, climate change, carbon dioxide reduction, greenhouse gases, and global warming.

Additionally, Taiwan ranked first in DDA and second in DDR for SDG 3. Major factors include active participation in international collaborative research such as the Global Burden of Disease, increased publications in international medical journals such as The Lancet, Journal of the American College of Cardiology, and the New England Journal of Medicine, and its response to COVID-19.

Japan traditionally has strengths in basic science and highly specialized higher education institutions and tends to have fewer opportunities for interdisciplinary initiatives. Additionally, Japanese universities and research institutions often maintain strict disciplinary boundaries (organizational or cultural), and interdisciplinary centers and flexible programs like those in the United States and Europe are not common. Furthermore, although this is gradually changing, each research unit is often led by a professor and operates independently. Even when multiple groups working on related themes exist within the same institution, they do not necessarily collaborate.

To overcome this situation, challenges must be addressed, including inter-field communication issues due to differences in terminology, problems with research organization and culture, and mechanisms for research funding and support. Strategic initiatives are needed going forward to foster innovation.