Obituary GIDEON J. MELLENBERGH (1938–2021)

Gideon Jan Mellenbergh (known as Don to his friends and colleagues) was born in Amsterdam on August 9, 1938, and passed away in the same city on March 27, 2021.Don was a major force in the Dutch psychometric community.He was one of the founders of the Interuniversity Graduate School of Psychometrics and Sociometrics (IOPS) that united the Ph.D. programs in the Netherlands and Flanders, and which he directed between 1987 and 2000.He was a member of the Royal Dutch Academy of Sciences (KNAW), served on the boards of the Netherlands Organization for Scientific Research and National Institute of Educational Measurement, and presided accreditation committees to evaluate Dutch and Flemish university programs.Don was a connecting figure who was able to build and maintain good relationships with all members of the Dutch psychometric community, even where there were passionate differences of opinion about psychometrics.He did not care for schools of thought; he only distinguished between good and bad research-and disliked the latter.This motivated a lifelong quest to improve research methods in psychology.Don attended Hervormd Gymnasium in Amsterdam, a six-year secondary school for gifted students with a curriculum consisting of six mandatory languages (including Greek and Latin), from which he graduated in 1957 with a specialization in the natural sciences and mathematics.After shortly considering to enroll in the college of physical education-Don was an accomplished basketball player-he attended the six-year psychology program at the University of Amsterdam.Don was not very impressed with the curriculum until he met Adriaan de Groot, a towering figure in postwar Dutch psychology and the founder of the university's Psychological Methods group.After his graduation in 1965, Don was appointed as Assistant Professor of Psychological Methods.His first job was at the Department of Exam Techniques, a precursor of the Dutch educational testing bureau Cito (which was also founded by De Groot).This department was headed by Robert van Naerssen, a psychometrician far ahead of his time (van den Brink & Mellenbergh, 1984), whose impact was, however, limited