Brain game apps are a multi-million dollar industry, but new research shows that companies like Lumosity may not have the science to back up their claims. As The Huffington Post reports, psychologists at George Mason University have published a new study suggesting the positive results of brain-training apps are likely a placebo effect.

Mental exercise programs like Lumosity and Peak boast that their games are developed with help from scientists. Previous reports, including studies funded by Lumosity, appear to support the claim that brain games improve cognitive function on some level. But there's still a great deal of skepticism within the scientific community. For their recent study, published online by the Proceedings of the National Academy of Sciences, the George Mason University researchers did something that most other studies had failed to do: control for placebo effects.

To gather subjects for the study, they posted two versions of the same flyer around campus. One advertised a "Brain Training and Cognitive Enhancement" study and claimed that brain exercises boost fluid intelligence, while the other made no mention of the content of the study.

The two groups of 25 participants played the same memory puzzle for an hour. After returning the next day, the group that had gone into the study without bias showed no improvement from the baseline test the day before. The group that went in knowing they would play games meant to improve brain function exhibited an improvement equivalent to five to 10 points on an IQ test. These results suggest that when brain-training games do work, the mental boost might be coming from the player's own self-fulfilling expectations rather than anything to do with the app itself.

The new study complicates much of the evidence many brain game apps have been citing to support their claims. After reaching out to the authors of 19 brain-training studies, the George Mason University team found that 17 of them may have inadvertently introduced bias to their participants by mentioning the term brain-training or other buzz words.

Earlier this year, Lumosity was hit with a $2 million fine by the Federal Trade Commission for deceptive advertising. The app, which charges up to $300 for a lifetime subscription, was accused by the FTC of preying on "consumers' fears about age-related cognitive decline, suggesting their games could stave off memory loss, dementia, and even Alzheimer’s disease," and that it "simply did not have the science to back up its ads." Despite the controversy, the app still has about 70 million users worldwide. As the industry continues to grow, study co-author Cyrus Foroughi tells The Huffington Post that he hopes their new research will lead to more reliable studies into its effectiveness down the road.

[h/t The Huffington Post]

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