Bad Science, good money?

So I stumpled across this article: I Used The Wonder Weeks App To Understand My Son’s Tantrums. (It might be a sponsored product review, judging from the overtly positive tone, but what do I know.) After reading the arcticle one might think that sounds like a great app, well think again! The wonder weeks app is based on the book “The Wonder Weeks” (OT: “Oei, ik groei!” dt.: “Oje, ich wachse!“) which was written by Frans Plooij & Hetty van de Rijt after they conducted only a single study in 1992[1]. In the study they conclude:

“If the regression and transition periods hold up against the scrutiny of follow-up research, it is our opinion that the information about difficultperiods should be made available to parents, perhaps in the form of developmental guidance courses.”

And then they published the book “Oei, ik groei!” in the same year, allowing for plenty of follow-up research, I guess.
When eventually a follow-up study was made by C. de Weerth and P. van Geert[2], it came to the following conclusion:

“No support has been found for the model of 10 regression periods described by van de Rijt-Plooij & Plooij (1992a),notwithstanding the fact that the original criteria were at various points significantly weakened”

Plooij did what every good scientist would do, he issued a press statement:

“Het is heel slecht voor de wetenschap dat dergelijke artikelen gepubliceerd worden. Het zet mensen op het verkeerde been (…) Nog erger is het dat zo’n artikel ook nog eens beloond wordt”[3]

“It’s very bad for science that such articles are published. It misleads people  (…) Even worse is the fact that such an article is also being rewarded”

Since nobody could agree to his unique interpretation of the scientific method, he stopped beeing a professor and went on to sell even more copies of his book. 1.5 million worldwide (if you believe their website) and it still sells (ranked Nr. 109 in Books on Amazon US, Nr. 199 in Books on Amazon germany).

So if you can’t do the science you can still make some moolah. Ain’t that great!


  1. Infantile regressions: Disorganization and the onset of transition periods
  2. Emotional instability as an indicator of strictly timed infantile developmental transitions
  3. Oei oei… ; Ontwikkelingstheorie Plooij weerlegd door eigen promovenda

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