Do brain-training exercises really work?

"A major limitation in what we have seen so far is that in order to change the brain in a meaningful and sustainable way, despite the fact that it's plastic, you really have to engage it in a very deep way. We need to develop far more immersive therapeutic video games, in addition to doing better studies," he said.

The latest strike in this battle of brain scientists comes from seven researchers who published a review paper in this month's edition of the journal Psychological Science in the Public Interest.

The paper claims that there does not appear to be enough evidence to support brain training's ability to boost cognition -- and that many studies that back brain training have some shortcomings.

"Our review suggests that there is little compelling evidence for real-world benefits of existing brain-training products," said Daniel Simons, a psychology professor at the University of Illinois and lead author of the paper.

The researchers analyzed more than 132 published and peer-reviewed papers often cited by brain-training companies and proponents as evidence that the practice is effective. They found that all of the published studies fell short of best practices when it comes to conducting scientific research, Simons said.

"Many studies are suggestive of benefits," the researchers wrote. "Yet most studies have lacked adequate controls for placebo effects, have tested sample sizes that are much too small, and have not fully reported and analyzed all outcome measures."

A separate study, published in the Proceedings of the National Academy of Sciences in July, pointed to placebo effects as a reason for some of the positive findings associated with brain training.

For the small study, researchers at George Mason University created two separate flyers inviting students to participate in their research.

One flyer had non-suggestive language, advertising the study as an opportunity for students to earn credits. The other advertised the study as a "brain training and cognitive enhancement" opportunity and mentioned, "numerous studies have shown working memory training can increase fluid intelligence."

Then, the researchers asked 25 students who responded to the non-suggestive flyer and 25 who responded to the brain-training flyer to participate in the same one-hour session of cognitive training. All of the participants completed a fluid intelligence test before and after the training.

The researchers discovered that the students who responded to the non-suggestive flyer had no improvement in their test scores. However, the students who responded to the suggestive brain-training flyer experienced a five- to 10-point increase on average in their test scores.

"I wasn't too surprised. After talking with others in the field, it was clear that methodological flaws could be leading to some of the positive outcomes in published work" supporting brain training, said Cyrus Foroughi, a cognitive scientist at the United States Naval Research Laboratory. He led the study as a graduate student at George Mason University.

But neuroscientist Henry Mahncke, the CEO of Posit Science, a brain-training software and services company, said that the small study on placebo effects was designed to produce a biased result -- and that there are several brain-training controlled trials that show a different outcome.

"There's study after study that are randomized placebo-controlled trials of brain-training, and in those studies, both groups of people have equivalent expectations that they're going to benefit. So if there is a placebo effect, it washes out across those groups," Mahncke explained, adding that he thinks the new review paper condemning brain-training research and programs is "silly."

Many of the scientific studies on brain training that Mahncke called high-quality -- including the largest cognitive-training intervention conducted yet, called ACTIVE, which involves 2,832 participants -- are the same ones picked apart in the new review paper.

"This is just a bunch of old-school psychologists, and what they've done is, they have theories from more than 100 years ago that explain why brain-training can't possibly work," he said of the new paper. "I've just never seen a less even-handed review."

Simons said he and his colleagues have decided not to publicly respond to Mahncke's comments.

One thing that Mahncke actually agrees with in the new review: Repeating a specific mental task, such as memorizing a list, does not result in generalized improvements in cognition.

As Simons, lead author of the new review paper, put it, "Different brain training companies propose different mechanisms."

"Most rely on the idea that training a basic cognitive mechanism using one task will lead not just to improved performance on that task but on all other tasks that rely on the same basic mechanism," he said. "We did not find compelling evidence that training on one task in one context generalizes to other tasks in other contexts."

And that's been showed over and over again in research, Mahncke said.

"So what have I learned about that as a scientist? Well, you probably shouldn't build training programs focused on practicing memory. Let's do something smarter than that, and we have done something smarter that," he said.

"There's been an absolute revolution, not in psychology but in neuroscience, over the past 30 years. What we've learned from this revolution in neuroscience is that the brain is what we call plastic. It's capable of changing itself, depending on what you do with it," he said, "and we can build on that idea of brain plasticity to build a new kind of brain-training program."

A Posit Science brain-training program called DriveSharp has been clinically proven to help the visual systems of older drivers to respond faster to hazards in their peripheral vision, Mahncke said. AAA has even partnered with Posit Science to offer the program to its members 55 and older at a discounted rate.

In the program, users complete visual attention tests and multiple object tracking tasks. Their risk of an at-fault crash can decrease by 48%, Mahncke said, citing a figure that was mentioned and questioned in the new review paper.

In the paper, the researchers wrote, "for the typical individual, the benefit works out to roughly one fewer at-fault crash every 62.5 years. ... The difference between at-fault and not-at-fault accidents is likely just noise due to the small number of crashes in this sample -- it is not particularly informative. From a consumer's perspective, the most relevant statistic is the probability of avoiding all crashes, and that does not vary meaningfully for a typical individual as a function of training. "

Nonetheless, such tested brain-training programs are the difference between brain games and brain training, according to Mahncke.

"There's a big line that I would draw, and that line would be between brain games and brain training. So, when we look out at the world, there's a lot of brain games out there," Mahncke said. "But what brain training is, is it takes a real systematic understanding of how the human brain works and how it's capable of change, and it builds exercises that directly target literally the way the brain processes information."

He added that the Federal Trade Commission has cracked down on brain gaming companies for making false claims about the science backing their programs.

"They went to those that had no science and no clinical data and said, 'Hey, you can't make claims about improving brain function if you don't have the data to back it up.' And that's what they did, and you know, that's a good thing for the field," he said.

In January, the creator of the brain-gaming company Lumosity agreed to pay $2 million to settle charges from the FTC. The charges alleged that Lumosity deceived consumers with unfounded claims that its games could sharpen thinking in everyday life and protect against cognitive decline.

The developers and marketers behind the LearningRx brain-gaming programs settled similar charges in May, paying $200,000.

Both Lumosity and LearningRx are still in business. On its website, Lumosity describes its web and mobile games as "designed by scientists to challenge core cognitive abilities." The company launched a collaborative research initiative called the Human Cognition Project that involves more than 40 universities.

Meanwhile, LearningRx's website notes, "We offer a variety of programs that target specific cognitive weaknesses." The company includes a five-member scientific advisory board and features more than a dozen studies about its programs on its website.

But the controversy surrounding brain training seems to have heated up before the two companies faced their charges, about two years ago, when critics called it "pseudoscience."

A group of 75 scientists and experts from institutions and universities around the world issued a statement in 2014 declaring that scientific evidence does not support claims that "brain games" help older adults boost their mental capabilities.

"We believed many of the claims made by the brain-training industry were misleading and in many cases patently false," said Laura Carstensen, founding director of the Stanford Center on Longevity and a psychology professor at Stanford University who was one of the scientists who signed the 2014 statement.

"Shortly after we issued the statement, the industry organized another statement and gathered signatures from other people who said that there was good evidence. Their statement got little attention from the scientific community ... but it left the public, once again, confused," she said.

Indeed, several months after the first statement was issued, an international group of about 133 scientists and practitioners countered that existing research supports the benefits of brain training.

Now, Mahncke said, "the recent review paper is just one more example of folks who are in the middle of a paradigm shift and don't realize it."

However, Gazzaley, the neuroscientist at UCSF, said that he views the paper as a call to action.

"When I read a review like that, I look at it as a call to arms. Here's the methodological challenges that we face as a field, and now, the task before us is to do this better, both on the technology development side and the scientific validation side. I remain cautiously optimistic about the future of this field," Gazzaley said.

He said that, in the future, there could be FDA-approved therapeutic video games for patients, and brain training programs in the form of virtual reality, augmented reality and wearables.

"But it will take a lot of high level of evidence to accomplish that. That's why the paper, to me, is a challenge to do better, and I think that's fair," he said.

Brain-training supporters believe that certain software and training programs can improve cognition, but how do the experts that question brain training recommend keeping a healthy brain?

"Stay physically and mentally active doing the activities that you enjoy. For example, if you enjoy reading and playing crossword puzzles, do that," Foroughi said.

Carstensen said that while there are many lifestyle changes -- from healthy eating to frequent exercise -- that someone can do to boost their brain, there is no quick fix.

"There is some evidence that physical exercise improves cognitive performance. Because heart health is related to brain health, diet is also likely involved. And there is considerable correlational evidence that people who are socially and cognitively engaged in stimulating lives, by working, volunteering or other forms of active learning, are in better shape cognitively than those who are not," she said. "But there is no evidence for magic bullets."