Because the Economist article quotes negative aspects of the report while ignoring the positive ones. The report says:
"Results indicate limited effects on academic achievement but positive impacts on cognitive skills and competences related to computer use. Cognitive abilities may arise through using the programs included in the laptops, given that they are aimed at improving thinking processes."
and found a quantitative improvement:
"students in the treatment group surpass those in the control group by between 0.09 and 0.13 standard deviations though the difference is only statistically significant at the 10 percent level for the Raven’s Progressive Matrices test (p-value 0.055). Still, the effects are quantitatively large. A back-of-the-envelope calculation suggests that the estimated impact on the verbal fluency measure represents the progression expected in six months for a child"
I would have summarized the study's results as something closer to "significant improvements in cognition were seen, but improvements against the Peruvian curriculum were not seen".
Yes, I read the report after that. RPM is cool and everything, but runs straight into the issue that it's easy to train RPM improvements of just 0.13 stddev - just do visual exercises and manipulations. (This is a big issue with interpreting dual n-back results.) And what is a laptop...?
Fundamentally, IQ tests are validated by their correlations with real world results (like the strong correlation with academic performance), and so any gains on IQ tests also require real world results if there's even a small chance of them being "hollow". (My standard example: you can improve your score on subtests by memorizing vocabulary, and this would improve your overall score. But has your underlying fluid intelligence increased? Probably not...)
And that's exactly what the small/null result for the academic scores shows.
And further, what we see especially (I'd say infamously) often with kid interventions is that the gains fade out within months or years. When tests are run in a few years, will we see even a 6-month gain on the RPM?
