With the increasing importance of interdisciplinary research, some studies have focused on the role of reference diversity by analysing reference lists of published papers. However, the relationship between the knowledge diversity of collaborating team members and research performance has been overlooked. In this study, we measured knowledge diversity through the disciplinary attributes of collaborating authors and research performance (understood as societal impact) through altmetric data. The major findings are: (1) The relationship between interdisciplinary collaboration diversity and societal impact is not a simple linear one, showing an inverted U-shaped pattern; and (2) As the number of collaborative disciplines increases, the marginal effects diminish or even become outweighed by the costs, showing a predominance of negative influences. Hence, diversity in interdisciplinary collaboration does not always have a positive impact. Research collaborations need to take into account the cost issues associated with the diversity of member disciplines.
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