One of the Netherlands' leading social psychologists made up or manipulated data in dozens of papers over nearly a decade, an investigating committee has concluded.
Diederik Stapel was suspended from his position at Tilburg University in the Netherlands in September after three junior researchers reported that they suspected scientific misconduct in his work. Soon after being confronted with the accusations, Stapel reportedly told university officials that some of his papers contained falsified data. The university launched an investigation, as did the University of Groningen and the University of Amsterdam, where Stapel had worked previously. The Tilburg commission today released an interim report (in Dutch), which includes preliminary results from all three investigations. The investigators found "several dozens of publications" in which fictitious data has been used. Fourteen of the 21 Ph.D. theses Stapel supervised are also tainted, the committee concluded.
Stapel issued a statement today in which he apologizes to his colleagues and says he "failed as a scientist" and is ashamed of his actions. He has cooperated to an extent by identifying papers with suspect data, according to university officials. The investigation by the three universities is ongoing and should ultimately investigate more than 150 papers that Stapel has co-authored, including a paper published earlier this year in Science on the influence of a messy environment on prejudice. "People are in shock," says Gerben van Kleef, a social psychologist at the University of Amsterdam, who did not work directly with Stapel. "Everybody wonders how this could have happened and at this proportion."
Stapel's work encompassed a broad range of attention-catching topics, including the influence of power on moral thinking and the reaction of psychologists to a plagiarism scandal. The committee, which interviewed dozens of Stapel's former students, postdoctoral researchers, co-authors, and colleagues, found that Stapel alone was responsible for the fraud. The panel reported that he would discuss in detail experimental designs, including drafting questionnaires, and would then claim to conduct the experiments at high schools and universities with which he had special arrangements. The experiments, however, never took place, the universities concluded. Stapel made up the data sets, which he then gave the student or collaborator for analysis, investigators allege. In other instances, the report says, he told colleagues that he had an old data set lying around that he hadn't yet had a chance to analyze. When Stapel did conduct actual experiments, the committee found evidence that he manipulated the results.
Many of Stapel's students graduated without having ever run an experiment, the report says. Stapel told them that their time was better spent analyzing data and writing. The commission writes that Stapel was "lord of the data" in his collaborations. It says colleagues or students who asked to see raw data were given excuses or even threatened and insulted.
At least two earlier groups of whistleblowers had raised questions about Stapel's work, the commission found. No one followed up on their concerns, however. Stapel's fabrications weren't particularly sophisticated, the committee says, and on careful inspection many of the data sets have improbable effect sizes and other statistical irregularities. His colleagues, when they failed to replicate the results, tended to blame themselves, the report says. Among Stapel's colleagues, the description of data as too good to be true "was a heartfelt compliment to his skill and creativity," the report says.
The report recommends that the universities of Groningen and Tilburg look into whether criminal charges are appropriate based on the misuse of research funds and possible harm to Stapel's students resulting from the fraud. The University of Amsterdam, where Stapel did his Ph.D., has apparently not been able to determine whether his thesis was fraudulent or not, in part because some of the original data records were destroyed. The committee suggests that the university consider revoking Stapel's degree, however, based on conduct that is "unbecoming" to the degree holder. (The University of Konstanz in Germany revoked disgraced physicist Jan Hendrik Schön's Ph.D. for that reason.)
UPDATE: The Dutch report noted in the article has now been released in an official English version. The report says that Diederik Stapel voluntarily identified a list of journal articles he authored or co-authored that were "based on fabricated data" but that list is not in the report and has not yet been made public.
Correction: This item has been changed to remove an inaccurate identification of what the whistle-blowers reported to university officials. It also notes that the committees will be investigating all of Stapel's publications, not just those since 2004.