Brain training games, like those made by NeuroNation and Lumosity, are marketed either explicitly or implicitly as a scientifically verified way to enhance your cognitive ability and to make you smarter. The creators of these games may not be happy with the latest science, however.

A spate of recent research articles shows that brain training can increase IQ, but a team of psychologists from George Mason University was concerned that this research is being confounded by the placebo effect. Any treatment in which the desired outcome is known ahead of time (e.g., pain reduction or, in this case, becoming smarter) is particularly susceptible to the placebo effect.

To test its hypothesis, the team recruited participants using two different posters. One of them was bland and boring (the "control" poster), and the other was overtly and enthusiastically promoting the benefits of brain training (the "placebo" poster).

Credit: Foroughi et al. PNAS 2016.

Participants were then asked to complete two pre-training intelligence tests and a one-hour cognitive training exercise. They were asked to return the next day to complete two more post-training intelligence tests. (See graphs.)

Credit: Foroughi et al. PNAS 2016. (Note: RAPM = Raven's Advanced Progressive Matrices; BOMAT = Bochumer Matrices Test)

As shown, participants in the placebo group, who were recruited by the poster extolling the benefits of brain training, saw a large (and statistically significant) improvement in their scores, equivalent to a 5- to 10-point increase on an IQ test. Furthermore, those in the placebo group were likelier to believe that intelligence is changeable, suggesting a self-selection bias among the people who responded to the placebo poster.

The takeaway message is not that brain training games are worthless, but that the method in which participants are recruited can greatly impact the outcome of a study. People who already believe in the benefits of brain training may be more likely to participate in a study that is explicitly about the benefits of brain training. Obviously, such self-selection will bias the results, and the placebo effect can magnify them. (The authors note that many published studies on brain training recruit participants with materials that likely encourage a self-selection bias.)

To be sure, keeping an active mind is widely believed to be important for maintaining mental health as we age. So, perhaps there is room for brain training games as part of a mental exercise regimen. Future studies aiming to determine the impact of these games on cognitive ability should be careful to control for selection bias and the placebo effect. As of now, however, the conclusion that brain training games are making people smarter appears to rest on shaky ground.

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Source: Cyrus K. Foroughi, Samuel S. Monfort, Martin Paczynski, Patrick E. McKnight, and P. M. Greenwood. "Placebo effects in cognitive training." PNAS. Published online: 20-June-2016. DOI: 10.1073/pnas.1601243113