The importance of matching: a case study

Earlier (ok, in the only previous, first post on this blog) I discussed the recent study of Zachary Horne et al. (2015), where they concluded that threatening communication may be an effective approach to counter anti-vaccination attitudes. One of the problems with this study was that the manipulation was not valid: the conditions differed on many variables, any of which may explain the results they found.

After I deliberated for a while whether to inform the authors of the blog post, I decided to do so in the spirit of academic debate, transparency, and learning from each other. He swiftly replied, and one of the things he dis was correct my assumption that they did not share their data. They did actually share their data! I think that’s very commendable – I strongly believe that all researchers should Fully Disclose. Zachary posted it at the excellent (and free) Open Science Framework repository, specifically at After having downloaded the data, I decided to write a brief follow-up post about matching of conditions and validity of manipulations. Continue reading “The importance of matching: a case study”

Countering antivaccination attitudes: don’t twiddle the dials before examining the engine

Recently, a number of media outlets enthusiastically reported that “Scare tactics may be the surest way to get parents to vaccinate their children“, suggesting to “Scare the crap out of [anti-vaccine parents]“, and happily claiming that “There’s a surprisingly simple way to convince vaccine skeptics to reconsider“.

Unfortunately, the study that these bold statements are based on, “Countering antivaccination attitudes” by Horne, Powell, Hummel and Holyoak and published in PNAS, suffers from a number of serious flaws. Continue reading “Countering antivaccination attitudes: don’t twiddle the dials before examining the engine”