Discovering a glaring error in a research paper – a personal account

New York Magazine has published a great article about how grad student Steven Ludeke tried to correct mistakes in the research of Pete Hatemi and Brad Verhulst. Overall, Ludeke summarises his experience as ‘not recommendable’. Back in my undergraduate years I spotted an error in an article by David DeMatteo and did little to correct it. Why?

Christian Bale playing a non-incarcerated American Psycho.

David DeMatteo, assistant professor in Psychology at Drexel University, investigates psychopathy. In 2010, I was a lowly undergraduate student and noticed a glaring mistake in one of his top ten publications which has now been cited 50 times according to Google Scholar.

The error

The study investigated the characteristics of psychopaths who live among us, the non-incarcerated population. How do these psychopaths manage to avoid prison? DeMatteo et al. (2006) measured their psychopathy in terms of personality features and in terms of overt behaviours. ‘Participants exhibited the core personality features of psychopathy (Factor 1) to a greater extent than the core behavioral features of psychopathy (Factor 2). This finding may be helpful in explaining why many of the study participants, despite having elevated levels of psychopathic characteristics, have had no prior involvement with the criminal justice system.’ (p. 142)

The glaring mistake in this publication is that Factor 2 scores at 7.1 (the behavioural features of psychopathy) are actually higher than the Factor 1 scores at 5.2 (the personality features of psychopathy). The numbers tell the exactly opposite story to the words.


The error in short. The numbers obviously do not match up with the statement.

The numbers are given twice in the paper making a typo unlikely (p. 138 and p. 139). Adjusting the scores for the maxima of the scales that they are from (factor 1 x/x_max = 0.325 < factor 2 x/x_max=0.394) or the sample maximum (factor 1 x/x_max_obtained = 0.433 < factor 2 x/x_max_obtained = 0.44375) makes no difference. No outlier rejection is mentioned in the paper.

In sum, it appears as if DeMatteo and his co-authors interpret their numbers in a way which makes intuitive sense but which is in direct contradiction to their own data. When researchers disagree with their own data, we have a real problem.

The reaction

1) Self doubt. I consulted with my professor (the late Paddy O’Donnel) who confirmed the glaring mistake.

2) Contact the author. I contacted DeMatteo in 2010 but his e-mail response was evasive and did nothing to resolve the issue. I have contacted him again, inviting him to react to this post.

3) Check others’ reactions. I found three publications which cited DeMatteo et al.’s article (Rucevic, 2010; Gao & Raine, 2010; Ullrich et al., 2008) and simply ignored the contradictory numbers. They went with the story that community dwelling psychopaths show psychopathic personalities more than psychopathic behaviours, even though the data in the article favours the exactly opposite conclusion.

4) Realising my predicament. At this point I realised my options. Either I pursued this full force while finishing a degree and, afterwards, moving on to my Master’s in a different country. Or I let it go. I had a suspicion which Ludeke’s story in New York Magazine confirmed: in these situations one has much to lose and little to gain. Pursuing a mistake in the research literature is ‘clearly a bad choice’ according to Ludeke.

The current situation

And now this blog post detailing my experience. Why? Well, on the one hand, I have very little to lose from a disagreement with DeMatteo as I certainly don’t want a career in law psychology research and perhaps not even in research in general. The balance went from ‘little to gain, much to lose’ to ‘little to gain, little to lose’. On the other hand, following my recent blog posts and article (Kunert, 2016) about the replication crisis in Psychology, I have come to the conclusion that science cynicism is not the way forward. So, I finally went fully transparent.

I am not particularly happy with how I handled this whole affair. I have zero documentation of my contact with DeMatteo. So, expect his word to stand against mine soon. I also feel I should have taken a risk earlier in exposing this. But then, I used to be passionate about science and wanted a career in it. I didn’t want to make enemies before I had even started my Master’s degree.

In short, only once I stopped caring about my career in science did I find the space to care about science itself.

— — —

DeMatteo, D., Heilbrun, K., & Marczyk, G. (2006). An empirical investigation of psychopathy in a noninstitutionalized and noncriminal sample Behavioral Sciences & the Law, 24 (2), 133-146 DOI: 10.1002/bsl.667

Gao, Y., & Raine, A. (2010). Successful and unsuccessful psychopaths: A neurobiological model Behavioral Sciences & the Law DOI: 10.1002/bsl.924

Kunert, R. (2016). Internal conceptual replications do not increase independent replication success Psychonomic Bulletin & Review DOI: 10.3758/s13423-016-1030-9

Rucević S (2010). Psychopathic personality traits and delinquent and risky sexual behaviors in Croatian sample of non-referred boys and girls. Law and human behavior, 34 (5), 379-91 PMID: 19728057

Ullrich, S., Farrington, D., & Coid, J. (2008). Psychopathic personality traits and life-success Personality and Individual Differences, 44 (5), 1162-1171 DOI: 10.1016/j.paid.2007.11.008

— — —

Update 16/11/2016: corrected numerical typo in sentence beginning ‘Adjusting the scores for the maxima…’ pointed out to me by Tom Foulsham via twitter (@TomFoulsh).



  1. “In short, only once I stopped caring about my career in science did I find the space to care about science itself”
    Exactly. This is because caring about one’s career and science too often conflict. And we’re back to the debate on the wrong incentives in science…

  2. This is one area in which I hope technology presents a means that can truly change the dynamic. Though people will always have a knee-jerk propensity to defend themselves the ability to actually revise, update, and share work more transparently (e.g. SSRN, arxiv, etc) could allow more “constructive” criticism. Obviously this case was a bit far gone for that, but it is something I hope will shift as the whole process of research => papers becomes more open.

  3. Better late than never, hey? But like you say, this has been cited fifty times. Other people must have read it thoroughly enough to notice the error and then also said nothing.

    It’s a shame that academia creates an atmosphere where junior academics won’t criticise obvious mistakes out of fear for their own career prospects. It’s also a shame that the publishing system means that it’s not possible for the authors to correct these mistakes without massive retraction or correction notices, which would also damage their own career prospects. Because sure, this is a mistake in a paper that needs to be corrected, but it doesn’t look like it’s deliberate malpractice or fraud or anything more sinister.

    I don’t think this is unique to academia, but it is something we need to figure out how to change. While I don’t like the closed, paid-for publishing system we currently have, I think this is a possible argument for it. Publishers are always talking about the added value that they provide in order to justify the APCs and/or massive subscription fees.

    Here, a genuinely valuable service would be a thorough, painstaking proofreading and correction process. If mistakes like this could be caught before publication, then you wouldn’t have had six years of agonising over whether reporting it would hurt your career, and the authors wouldn’t have to deal with the bad publicity that comes from acknowledging and correcting their mistake. Protecting people’s careers might actually be a service worth paying publishers for… but the fact is that this wasn’t caught by the publishers either, despite charging for the proofreading services they provide, so I think a lot of the blame goes to them as well.

  4. As a research assistant I watched first-hand as a rising prof challenged methodological flaws in foundational papers. He found the vitriol and promises of ruining his career entertaining and motivating. I found it disillusioning and left academic research for applied research. I’d rather have my politics and biases upfront and documented rather than sabotaged or concealed by a small group of researchers that dominate the review boards and “ethics” committees.

Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s