In October, Stanford University’s Center for Longevity and the Max Planck Institute for Human Development in Berlin asked a group of more than 70 neuroscientists, cognitive psychologists, and academics to share their views on these games. “There is little evidence that playing brain games improves underlying broad cognitive abilities, or that it enables one to better navigate a complex realm of everyday life,” the group wrote in a consensus report.

The validity of brain games has been a point of debate ever since the first iterations of them launched in the early 2000s. What’s notable about the Stanford/Max Planck report is its deliberation and scope, offering insight collected over the course of a year from experts based at 40 institutions in six different countries. (Disclaimer: I'm a research engineer in a physics laboratory based at Stanford University. However, my work is unrelated to the subject matter in the report.)

The report questions the “pernicious,” “exaggerated,” and “misleading” claims made by brain-game manufacturers and stresses that wide-reaching positive results are “elusive.” The signatories don’t call out any specific types of brain-training software, but their language is often damning. “Many scientists cringe at exuberant advertisements claiming improvements in the speed and efficiency of cognitive processing and dramatic gains in ‘intelligence,’” they write.

Brain training is projected to be a $3 billion industry by 2015. Its target demographic is vast, from kids lagging behind in school to seniors who’d love to be able to remember things more efficiently. Most people, in fact, would appreciate the opportunity to feel like they’re getting the most out of their brains, and when a particular product is advertised as being both educational and backed by science, it can be hard to resist.

That there’s a need for scientists to issue a signed letter like this one only goes to show how popular brain games are and to what extent experts feel the public may have been seduced by the promise that they’re endorsed by science. The letter is both a word of caution to the public and the signatories’ way of distancing themselves from the commercial products. It's one thing to advertise Kool-Aid, the letter seems to say. But it's quite another to say people should drink it because science says so.

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The brain's plasticity has been a matter of discussion in scientific circles for more than a century. In 1890, the American doctor William James discussed the “extraordinary degree of plasticity” in nerve tissue in his book, The Principles of Psychology. James wrote that “the phenomena of habit in living beings are due to the plasticity,” and concluded that this shaping of the brain's neurons is the foundational mechanism for growing and learning. His work caught the eye of Edward Lee Thorndike. Over the course of the next 50 years, Thorndike became one of the most renowned educational psychologists, known for his experimental approaches to the field.