An app that improves fluid intelligence – the kind of smarts that help you solve unfamiliar problems – is the holy grail of the billion-dollar brain training industry. Not only would such an app give you an intellectual edge, but it could stave off the mental decline caused by ageing.
Or so the thinking goes.
But the positive effects seen in some brain training studies could be little more than a placebo effect induced by sloppy recruitment practices, according to a new study.
The placebo effect occurs when a person’s belief in a treatment leads to an improvement in their condition even when the treatment is a sham. So powerful is the effect that drug trials traditionally include placebos to ensure any benefits of the drugs being tested are real.
Cognitive scientist Cyrus Foroughi and colleagues at George Mason University in the US decided to test whether brain-training studies also fall prey to the placebo effect.
Their findings suggest they do.
Foroughi and colleagues recruited university students using two different flyers. The first invited participants for a “brain training and cognitive enhancement” study, stating that “numerous studies have shown working memory training can increase fluid intelligence”.
The second, non-suggestive flyer offered credit points for participation but didn’t state the study’s purpose.
Participants completed an hour of cognitive training. Fluid intelligence was tested before, and then again on the day after training.
Participants recruited using the suggestive flyers saw the equivalent of a five to 10-point bump to their IQ – at the high end of brain training effects. Those recruited with the non-suggestive flyers missed out on the benefits.
“It’s strong evidence that it wasn’t really a true training effect,” says Foroughi.
The sort of suggestive recruitment Foroughi and his colleagues used to induce the placebo effect is common in brain training research.
The team tracked down recruitment procedures for 19 recent studies and found that all bar two explicitly recruited participants for a cognitive or brain training study.
This potentially biases research by favouring the recruitment of people who easily succumb to the power of positive expectation.
The placebo effect will need to be taken into account in future study design, says Foroughi.