Dear IOPS members,

Don Mellenbergh passed away on 27 March. Don Mellenbergh was one of the founding fathers and directors of IOPS. He was Emeritus Professor of Psychological Methods at the University of Amsterdam. He was born august 9 1938, studied Psychology at the University of Amsterdam and obtained his PhD under supervision of A.D. de Groot. He worked at the University of Amsterdam and University of Utrecht and was full professor at the University of Amsterdam from 1982-2003. He was also a member of the Royal Netherlands academy of Arts and Sciences (KNWA), and Editor of Psychometrika.

Don Mellenbergh published many papers on measurement in the behavioural sciences notably on test theory, utility, and validity. He developed the concept of item bias, coining the distinction between uniform and non-uniform bias, and laid a cornerstone for the now standard unified view of psychometric models with his famous publication on Generalized Linear
Item Response Theory. Perhaps even more important were his contributions to the social fabric of methodology. Mellenbergh acted as promotor of dozens of psychometricians, including Wim van der Linden, Henk Kelderman, and Denny Borsboom, and took the initiative to unite Dutch methodologists in IOPS.

Don Mellenbergh was a warm and friendly colleague. He was hardly interested in status, and as a social mover (Don was the son of a taxi driver) he continued to support equal opportunities for different groups throughout his life. Don always insisted that IOPS exists for the Ph.D. students, not for the staff, and regularly made this clear in practice. For example, at an IOPS conference in Maastricht in the 1990s where there were two hotels available – a regular one and a high class one – Don did not hesitate and reserved all the rooms in the high class hotel for the Ph.D. students.
Don Mellenbergh was passionate about his work, and after his retirement could frequently be found at the department of Psychological Methods of the University of Amsterdam. He published his last book, Counteracting methodological errors, in 2019 – sixteen years after his retirement – and at the time of his death was working on a book that documented changes in
academia over the past decades.

Don’s striking voice can be heard in the following interview: https://www.adng.nl/nl/interview/don-mellenberg/

We will remember Don as a very influential psychometrician that shaped our profession to the flourishing field it is today, a role model to many of today’s psychometricians, and a warm, supportive colleague whose spirit filled many IOPS conferences with joy and enthusiasm.

On behalf of Rob Meijer,
Chair of the IOPS board