Sampling bias and a belief in malleable intelligence may be behind small IQ changes

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But what of the initial research that suggested slight positive effects of such brain training? While brain training companies have publicly taken heat for their hyped-up claims, recent scientific reviews of the literature have largely upheld the initial findings. In fact, a 2015 meta-analysis concluded that the training could increase IQ scores by three to four points.

With a new report published Monday in the Proceedings of the National Academy of Sciences, that research might be nearing a blistering rebuff of its own.

In a study designed to assess the experimental methods of earlier brain-training studies, researchers found that sampling bias and the placebo effect explained the positive results seen in the past. “Indeed, to our knowledge, the rigor of double-blind randomized clinical trials is nonexistent in this research area,” the authors report. They even suggest that the overblown claims from brain training companies may have created a positive feedback loop, convincing people that brain training works and biasing follow-up research on the topic.

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http://arstechnica.com/science/2016/06/billion-dollar-brain-training-industry-a-sham-nothing-but-placebo-study-suggests/