Diederik Alexander Stapel (born 19 October 1966 in Oegstgeest, western Netherlands), is a former professor of social psychology at Tilburg University and before that at the University of Groningen in the Netherlands. In 2011 Tilburg University suspended Stapel, pending further investigation, for fabricating and manipulating data for his research publications. This scientific misconduct took place over a number of years and affected at least 55 publications.
Stapel obtained an M.A. cum laude in psychology and communications from the University of Amsterdam (UvA) in 1991. In 1997 he obtained his Ph.D. cum laude in social psychology from the UvA. He became professor at the University of Groningen in 2000 and moved to Tilburg University in 2006, where he founded TiBER, the Tilburg Institute for Behavioral Economics Research. In September 2010, Stapel became dean of the social and behavioral sciences faculty.
Stapel received the "Career Trajectory Award" from the Society of Experimental Social Psychology in 2009, which has since been retracted. He returned his Ph.D. title to the University of Amsterdam in November 2011, noting that his "behavior of the past years are inconsistent with the duties associated with the doctorate".
In September 2011, Tilburg University suspended Stapel from his duties, because he was suspected of using faked data for his research publications. The university announced an investigation of his work.
On 31 October 2011, a committee entrusted with investigating "the extent and nature of the breach of scientific integrity committed by Mr D.A. Stapel", formed by the Rector Magnificus of Tilburg University and chaired by Willem ("Pim") Levelt, published an interim report regarding Stapel's activities at the three Dutch universities where he had worked. The interim report pointed to three unidentified "young researchers" as the whistleblowers for the case, and implies that these whistleblowers spent months making observations of Stapel and his work before they concluded that something actually was wrong. The report also cites two professors who claim they had previously seen examples of Stapel’s data that were “too good to be true”. The report concluded that Stapel made up data for at least 30 publications. His general method towards the end of his career was to develop a complete experiment at the level of theory, hypotheses, methods, stimuli, questionnaires, and even participants' rewards- and then pretend that he would run the experiments at schools to which only he had access. Instead of doing so, he would make up the data and send these to colleagues for further analysis. The report also stated that earlier in his career, going back at least to 2004, he appears to have manipulated data rather than faked them. In all cases he acted alone and the report did not find any indication that coauthors, PhD students, or others were aware even in instances where suspicion may have been reasonable. On page 6-7, the interim report names 19 Ph.D. theses prepared with data delivered by Stapel. Of those, seven have been cleared. There are various degrees of suspicion about the remaining 12. The report advised that the Ph.D. degrees of the students involved should not be retracted.
It became widely known that Stapel treated his graduate students unfairly, with most of them graduating without ever actually completing an experiment. Stapel controlled the data in his lab, and when students asked to see the raw data, they were often given excuses. According to the report, there were occasions when Stapel’s data were given to an assistant to be entered into a computer. This assistant would then return the data file to Stapel. The researcher analyzing the data would then receive the file directly from Stapel. Stapel would apparently tell this researcher to, “Be aware that you have gold in your hands.” The report also suggests that Stapel elected to present a list of publications that contained fictitious data.
The interim report stated that it was not possible to determine whether Stapel fabricated or manipulated data for his 1997 dissertation at the University of Amsterdam, because the data had been destroyed. The university announced that it would investigate whether it would be possible to retract Stapel's Ph.D. because of exceptionally unworthy scientific behavior. Stapel has since returned his degree himself (see above).
The interim report stated that Stapel had caused severe damage to young people at the beginning of their careers, as well as to the general confidence in science, in particular social psychology. The University of Tilburg announced that it would pursue criminal prosecution of Stapel.
An extensive report investigates all of Stapel's 130 articles and 24 book chapters. A website was set up on 27 March 2012) to publish intermediate findings. According to the first findings, on the first batch of 20 publications by Stapel, studied by the "Levelt Committee", 12 were falsified and three contributions to books were also fraudulent. de Volkskrant reported that the final report was due on 28 November 2012, and that a book by Stapel (Ontsporing, "Derailment") was to be released around the same time.
Coping with chaos
A month after Tilburg University announced that it had found evidence of fraud in Stapel’s work, the journal Science posted a retraction notice on Stapel’s co-authored paper entitled Coping with chaos: How disordered contexts promote stereotyping and discrimination. The report from Science says:
- Our Report “Coping with chaos: How disordered contexts promote stereotyping and discrimination” (1) reported the effects of the physical environment on human stereotyping and discriminatory behavior. On 31 October 2011, the University of Tilburg held a press conference to announce findings of their investigation into possible data fraud on the part of author Stapel. These findings of the university’s interim report (2) included fabrication of data in this Science paper. Therefore, we are retracting the paper, with apologies from author Stapel. Coauthor Lindenberg was in no way involved in the generation of the data, and agrees to the retraction of the paper.
In December 2011, Stapel retracted this paper, the first to be retracted. The journal expressed initial concern regarding the paper's validity on November 1. In a response to the retraction, coauthor of the Chaos paper Siegwart Lindenberg told the journal in an email, “Stapel’s doing had caught me as much by surprise as it did anybody else. I never had any suspicion. He was a very trusted man, dean of the faculty, brilliant, successful, no indications for me to be distrustful. In this, I was not the only one. I also had no trouble with the results of the experiments.”
Meat eaters more selfish than vegetarians
The research result, obtained by Stapel and co-workers Roos Vonk (Radboud University) and Marcel Zeelenberg (nl) (Tilburg University), that meat eaters are more selfish than vegetarians, which was widely published in Dutch media, is suspected to be based on faked data. The research result had not yet been published in a scientific journal, only a press bulletin was released.
Reaction by Stapel
Responding to the interim report, Stapel stated:
I failed as a scientist. I adapted research data and fabricated research. Not once, but several times, not for a short period, but over a longer period of time. I realize that I shocked and angered my colleagues, because of my behavior. I put my field, social psychology in a bad light. I am ashamed of it and I deeply regret it.
... I think it is important to emphasize that I never informed my colleagues of my inappropriate behavior. I offer my colleagues, my PhD students, and the complete academic community my sincere apologies. I am aware of the suffering and sorrow that I caused to them.... I did not withstand the pressure to score, to publish, the pressure to get better in time. I wanted too much, too fast. In a system where there are few checks and balances, where people work alone, I took the wrong turn. I want to emphasize that the mistakes that I made were not born out of selfish ends.
In his memoirs that were published in November 2012 Stapel admits his fraud, but protests against the accusation in the interim report that he was a cunning, manipulative fraud with a plan.
Reaction in academia
On 28 November 2012 the joint final report, from the three investigating committees, was published.
It has been suggested that Stapel was able to continue his fraud for so long because of his status. At Tilburg he was "considered a star" and was seen by his colleagues and students as "charismatic, friendly and incredibly talented". Many students became his personal friends. But the final Levelt report raises more controversial questions about the ways in which Stapel went unchallenged for so long. The report concludes that there was "a more general failure of scientific criticism in the peer community and a research culture that was excessively oriented to uncritical confirmation of one’s own ideas and to finding appealing but theoretically superficial ad hoc results". It goes on to suggest that "not infrequently reviews [of social psychology journal articles] were strongly in favour of telling an interesting, elegant, concise and compelling story, possibly at the expense of the necessary scientific diligence."
This aspect of the report has been criticised by the Social Psychology Section of the British Psychological Society. In a letter to the Times Higher Education Supplement, on behalf of the Section, Stephen Gibson at York St John University, points out ".. there are no grounds for concluding either that research fraud is any more common in social psychology than other disciplines or that its editorial processes are particularly poor at detecting it", adding that: "Our sub-discipline does not deserve the harm to its reputation that may be provoked by the careless implication of unique deficiencies." The Levelt report has also been criticised by the European Association of Social Psychology in an open letter to its members.
In the February 2013 issue of The Psychologist, Willem Levelt, together with the chairs of the other two investigating committees, published a rejoinder to these and other criticisms. Drenth et al. acknowledge that they did not compare the situation in social psychology with other disciplines, but note that "such a comparative investigation was not part of the Committees’ commission."
In a review for the Association for Psychological Science, Stapel’s 315-page memoirs, entitled Ontsporing ("Derailed"), is described by Dutch psychologists Denny Borsboom and Eric-Jan Wagenmakers as "priceless and revealing". Stapel recounts that his misdemeanours began when he was sitting, alone in his office in Groningen, and he changed "an unexpected 2 into a 4". The reviewers describe the final chapter of the book as "unexpectedly beautiful" but note that it is full of lines taken from the works of writers Raymond Carver and James Joyce.
The research in which Stapel collaborated, and of which he was sole author, covers a wide range of topics.
In Categories of Category Accessibility: The Impact of Trait Concept versus Exemplar Priming on Person Judgments, a paper published in January 1997, Stapel is exploring the differences and similarities between priming traits and priming antonyms. This study, consisting of five different studies, shows that the judgments of a person are not just affected by the priming of relevant traits but by priming the antonyms of these traits. It was found that the effect of priming traits or antonyms was related to whether the inferences were relevant or irrelevant, to what extent they were evaluated, whether they were personal or behavioral, and whether the information found was enough to judge the subject. The paper was published by the Journal of Experimental Social Psychology, and lists Diederik A. Stapel, Willem Koomen, and Joop van der Pligt as authors.
In Similarities and Differences between the Impact of Traits and Expectancies: What Matters Is Whether the Target Stimulus Is Ambiguous or Mixed, a paper published in May 1998, Stapel studies the basis behind when a person has a stereotypical reaction to something that allows you to judge the subject based on their category of personality. This stereotyping either results in assimilation of the stereotypical testing or it results in contrast. The way to test this was by getting the same trait category model, a different trait category model, and matching the subject’s social category to the activated stereotype. This testing led to the findings that accessible stereotype knowledge can lead to fully known stereotypical judgments and counter stereotypical judgments. The paper was published by the Journal of Experimental Social Psychology, and lists Diederik A. Stapel, and Nobert Schwarz as authors.
In Interpretation versus Reference Framing: Assimilation and Contrast Effects in the Organizational Domain, a paper published in November 1998, Stapel is studying whether the type of information activated will get different judgments on the subject. Nonperson models are generally willing to show their influence during impression formation, while person models are more willing during the judgment phase because they are similar to the target they are being compared to. Stapel found that as primed category information is used there are judgments of ambiguous affects. When category information is used there are contrastive judgments. The paper was published by Organizational Behavior and Human Decision Processes, and lists Diederik A. Stapel and Willem Koomen as authors.
In Hardly thinking about others: On Cognitive Busyness and Target Similarity in Social Comparison Effects, a paper published in May 2006, Stapel studies a person’s comparison of themselves and another, and the dependencies on the level of similarity between the two. The paper cites that when a strong similarity was recognized, the subject would provide little contrast between themselves and of the person involved in their comparison. The example given is, “I feel smart because my sister won the Pulitzer prize.” When moderate similarity was recognized the subject provided a moderate contrast between themselves and the person. The example given is, “I feel stupid because my colleague is an excellent chess player.” Finally, when there was little or no similarity recognized, the greatest contrast was experienced. The example given is, “I do not feel less attractive when thinking of Cindy Crawford because she is a professional model and I am a psychologist.” The paper mentions experimentation based on when the subjects were cognitively busy or unable to devote a lot of time to make a comparison. The paper was published by the Journal of Experimental Social Psychology, and cites Diederik A. Stapel, and David M. Marx as authors.
In The flexible Unconscious: Investigating the Judgmental Impact of Varieties of Unaware Perception, a paper published in January 2006, Stapel discusses how the accessibility of information affects the judgment of a subject. When information is readily accessible the subject usually makes a contrastive comparison between the new and familiar stimuli. When the information is moderately accessible they are usually assimilative, not placing either the new or familiar stimuli above the other, but giving them equal status. When there is little information provided, there is little comparison made between new and familiar stimuli, and such comparison is often unimportant. The practical uses discussed in this study include examples of advertisements of a product. In general, the more information and exposure someone has to a product, the more likely they are to believe that the product is better than other brands. The paper was published by the Journal of Experimental Social Psychology, and cites Diederik A. Stapel and Willem Koomen as authors.
Selected scientific publications
- — Koomen, Willem (2001). "I, we, and the effects of others on me: How self-construal moderates social comparison effects". Journal of Personality and Social Psychology 80 (5): 766–781. doi:10.1037/0022-35220.127.116.116. PMID 11374748.
- — Koomen, Willem (2001). "When we wonder what it all means: Interpretation goals facilitate accessibility and stereotyping effects". Personality and Social Psychology Bulletin 27 (8): 915–929. doi:10.1177/0146167201278001.
- This paper is one of three retracted by the journal.
- — Tesser, A. (2001). "Self-activation increases social comparison". Journal of Personality and Social Psychology 81 (4): 742–750. doi:10.1037/0022-3518.104.22.1682. PMID 11642358.
- — Koomen, Willem; Ruijs, K. (2002). "The effects of diffuse and distinct affect". Journal of Personality and Social Psychology 83 (1): 60–74. doi:10.1037/0022-3522.214.171.124. PMID 12088133.
- — (2003). "Making sense of hot cognition: Why and when description influences our feelings and judgments". In Forgas, J.P; Williams, K.D.; von Hippel, W. Social judgments: Implicit and explicit processes. New York, NY, USA: Cambridge. pp. 227–250.
- — Siegwart Lindenberg, S. (8 April 2011). "Coping with Chaos: How Disordered Contexts Promote Stereotyping and Discrimination". Science 332 (6026): 251–253. doi:10.1126/science.1201068.
- Stapel, Diederik; Ontsporing ("Derailment"); Prometheus Books, November 2012; ISBN 9-04462-312-5
- Frank van Kolfschooten (nl); Ontspoorde wetenschap ("Derailed Science"); De Kring publishers; October 2012; ISBN 9-49156-702-0
- "Diederik Stapel succeeds Theo Verhallen as Dean of the Tilburg School of Social and Behavioral Sciences". Tilburg University. 7 July 2010. Retrieved 17 September 2011.
- "Levelt: fraud detected in 55 publications | Univers". Universonline.nl. 2012-11-28. Retrieved 2013-03-01.
- "Diederik Stapel succeeds Theo Verhallen as Dean of the Tilburg School of Social and Behavioral Sciences". Tilburg University. 8 July 2010. Retrieved 5 October 2011.
- "Career Trajectory Award Recipients". Society of Experimental Social Psychology. Retrieved 1 November 2011.
- Redactie. "Stapel doet vrijwillig afstand van doctorstitel - Binnenland - VK". Volkskrant.nl. Retrieved 2011-11-17.
- "Prof. Diederik Stapel suspended" (Press release). Tilburg University. 7 September 2011. Retrieved 17 September 2011.
- Enserink, Martin (7 September 2011). "Dutch university sacks social psychologist over faked data". Science. Retrieved 17 September 2011.
- Levelt Committee (31 October 2011). "Interim Report Regarding the Breach of Scientific Integrity by Prof. D. A. Stapel" (PDF). Tilburg University. Retrieved 17 January 2012.
- Levelt, Oct. 2011, p. 9
- Levelt, Oct. 2011, p. 6.
- "Diederik Stapel: The Lying Dutchman". The Washington Post (Post Opinions). 1 November 2011. Retrieved 17 January 2012.
- "Commissie onderzoekt Amsterdamse werk Stapel - Nieuws en Agenda - Universiteit van Amsterdam" (in (Dutch)). Uva.nl. 23 September 2011. Retrieved 2011-11-17.
- Levelt, Oct 2011, p. 20
- "UvA onderzoekt mogelijkheid intrekken doctorsgraad Stapel - Nieuws en Agenda - Universiteit van Amsterdam" (in (Dutch)). Uva.nl. 31 October 2011. Retrieved 2011-11-17.
- Callaway, Ewen; Lindenberg, S. (8 December 2011). "Report finds massive fraud at Dutch universities : Nature News". Nature.com 332 (6026): 251. doi:10.1126/science.1201068. Retrieved 2011-11-17.
- "First committee findings damn fraudulent Tilburg professor". Dutchnews.nl. Tuesday 27 March 2012.
- "Stapel Investigation website", Joint Tilburg/ Groningen/ Amsterdam investigation of the publications by Mr. Stapel
- "Diederik Stapel heeft nooit zijn excuses aangeboden" (in Dutch). Nu.nl. 28 maart 2012.
- "Hoe heeft Stapel de wetenschappelijke wereld voor de gek kunnen houden?". de Volkskrant (in Dutch). 28 November 2012. Retrieved 28 November 2012.
- Marcus, A. (1 December 2011). "Science drops other shoe in Stapel case, retracts recent paper on chaos". Retraction Watch. Retrieved 17 January 2012.
- Callaway, E. (1 December 2011). "Dutch psychology fraudster issues first retraction.". Nature (Nature News Blog). Retrieved 17 January 2012.
- "Meat eaters are selfish and less social". DutchDailyNews.com. 30 August 2011. Retrieved 17 September 2011.
- "Meat eaters absolved, professor in the dock". DutchNews.nl. 8 September 2011. Retrieved 17 September 2011.
- Vanheste, Thomas (13 September 2011). "Onder psychologen" (in Dutch). Vrij Nederland. Retrieved 31 October 2011.
- "Stapel betuigt openlijk 'diepe spijt'". Brabants Dagblad. 31 October 2011. Translated from Dutch: "Ik heb gefaald als wetenschapper, als onderzoeker. Ik heb onderzoeksgegevens aangepast en onderzoeken gefingeerd. Niet een keer, maar meerdere keren, en niet even, maar gedurende een langere tijd. Ik realiseer me dat ik door dit gedrag mijn directe collega's in verbijstering en boosheid heb achtergelaten en mijn vakgebied, de sociale psychologie, in een kwaad daglicht heb gesteld. Ik schaam me daarvoor en ik heb daar grote spijt van.
...Ik hecht er aan te benadrukken dat ik hen nooit op de hoogte heb gebracht van mijn oneigenlijk gedrag. Ik bied mijn collega's, mijn promovendi en de gehele academische gemeenschap mijn oprechte excuses aan. Ik ben me bewust van het leed en het verdriet dat ik bij hen heb veroorzaakt.
... Ik heb de druk te scoren, te publiceren, de druk om steeds beter te moeten zijn, niet het hoofd geboden. Ik wilde te veel te snel. In een systeem waar er weinig controle is, waar mensen veelal alleen werken, ben ik verkeerd afgeslagen. Ik hecht eraan te benadrukken dat de fouten die ik heb gemaakt, niet zijn voortgekomen uit eigenbelang."
- Levelt Committee, Noort Committee, Drenth Committee (28 November 2012). "Flawed science: The fraudulent research practices of social psychologist Diederik Stapel". Retrieved 14 February 2013.
- Jarrett, C., "Stapel - final report", in The Psychologist (News), Vol 26, Part 2 (February 2013), p. 88
- Drenth, P., Levelt, W. and Noort, E., "Flawed science?", in The Psychologist (Letters), Vol 26, Part 2 (February 2013), pp. 80-81
- Stapel, DA; Koomen, W; van der Pligt, J. (January 1997). "Categories of Category Accessibility: The Impact of Trait Concept versus Exemplar Priming on Person Judgments". Journal of Experimental Social Psychology 33 (1): 47–76. doi:10.1006/jesp.1996.1311. Retrieved 17 January 2012.
- Schwarz, N; Schwarz, Norbert (May 1998). "Similarities and Differences between the Impact of Traits and Expectancies: What Matters Is Whether the Target Stimulus Is Ambiguous or Mixed". Journal of Experimental Social Psychology 34 (3): 227–245. doi:10.1006/jesp.1997.9997. Retrieved 17 January 2012.
- Stapel DA, Koomen W. (November 1998). "Interpretation versus Reference Framing: Assimilation and Contrast Effects in the Organizational Domain". Organizational Behavior and Human Decision Processes 76 (2): 132–148. doi:10.1006/obhd.1998.2802. PMID 9831519. Retrieved 17 January 2012.
- Stapel DA, Marx DM. (May 2006). "Hardly thinking about others: On Cognitive Busyness and Target Similarity in Social Comparison Effects". Journal of Experimental Social Psychology 42 (3): 397–405. doi:10.1016/j.jesp.2005.05.006. Retrieved 17 January 2012.
- Stapel DA, Koomen W. (January 2006). "The flexible Unconscious: Investigating the Judgmental Impact of Varieties of Unaware Perception". Journal of Experimental Social Psychology 42 (1): 112–119. doi:10.1016/j.jesp.2005.02.002. Retrieved 17 January 2012.
- "Retraction of "Terror Management and Stereotyping: Why Do People Stereotype when Mortality is Salient?," "Distinctiveness is Key: How Different Types of Self-Other Similarity Moderate Social Comparison Effects," and "When We Wonder What It All Means: Interpretation Goals Facilitate Accessibility and Stereotyping Effects"". Personality and Social Psychology Bulletin 39 (2): 264. February 2013. doi:10.1177/0146167212474240. PMID 23386661.
- Kreulen, Edwin (1 November 2011). "Diederik Stapel verzon list na list en duldde geen enkele tegenspraak". Trouw.nl. "(English translation) Stapel knew at that moment exactly what he expected, which could be inferred yesterday from the words of Pim Levelt. 'The science article is based on fake data', was his verdict, just like at least 29 other publications by Stapel, and probably more. (Dutch original) Stapel wist op dat moment precies wat hij verwachtte, viel gisteren af te leiden uit de woorden van onderzoeker Pim Levelt. 'Het Science-artikel berust op gefabriceerde gegevens', was zijn oordeel, net als in ieder geval 29 andere publicaties van Stapel, en vermoedelijk nog meer."
- Stapel, D. A.; Lindenberg, S. (2 December 2011). "Retraction". Science 334 (6060): 1202. doi:10.1126/science.334.6060.1202-a.
- Alberts, Bruce (11 November 2011). "Editorial Expression of Concern". Science 334 (6057): 760. doi:10.1126/science.1216027.
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- Article by Roos Vonk on her website about the "meat research" (Dutch)
- Omroep Brabant (Dutch)
- Interim report by the Levelt committee that has investigated the fraud, dated 31st Oct. 2011 (Dutch)
- Résumé Diederik Stapel published on stapel.socialpsychology.nl in 2006
- List of publications by Stapel
- "Noted Dutch Psychologist Stapel Accused of Research Fraud" in The New York Times
- Final Report: Stapel Affair; Points to Bigger Problems in Social Psychology by Martin Enserink on 28 November 2012 in Science Magazine
- Final report by the Levelt, Noort and Drenth committees 28 Nov. 2012
- Reaction to the Final report by the European Association of Social Psychology See European Association of Social Psychology
- The sin of bad science in Financial Times December 21, 2012 by Simon Kuper
- The Psychology of Lying: Diederik Stapel's audacious academic fraud. in the New York Times Magazine on 26 April 2013 by Yudhijit Bhattacharjee