April 29, 2008
Scientific American
Tabitha M. Powledge

In the market for more brain power? In what’s being touted as “a landmark” result, University of Michigan at Ann Arbor (U.M.) researchers report that a specific memory exercise may improve so-called fluid intelligence—the capacity to succeed at new cognitive tasks and in new situations. The finding flies in the face of conventional wisdom in psychology that training for one brain task cannot be transferred to improvement in other mental abilities. If proved, the finding could lead to new therapies and prevention of learning disorders and age-related memory loss.

The study, published in the journal Proceedings of the National Academy of Sciences USA, contradicts decades of research showing that attempts at crossover training effects, known as far transfer, do not work well. Previous research has shown that improving on one kind of cognitive task does not improve performance on other kinds—for example, memorizing long strings of numbers does not help people learn strings of letters.

“This is the first time it could be shown that cognitive training leads to improvement on an untrained task, so we can say it’s a far-transfer task,” says study co-author Martin Buschkuehl, a U.M. psychologist. He and his colleagues are hoping to extend the work beyond the healthy 20-something adults they studied to other groups, such as older people in the throes of cognitive decline and youngsters diagnosed with attention-deficit disorder.

“It’s a little oversold, but it is certainly interesting,” says Earl Hunt, a psychologist at the University of Washington in Seattle, who researches individual differences in cognition but was not involved in this study. “It will be important in education and a number of other things—if these results prove to hold up.”

Researchers gave 35 volunteers a standardized intelligence test and gave them another such test after training them on a complex memory task for a variable number of days (eight, 12, 17 or 19). Thirty-five other study participants simply took the tests. Both improved on the second one, but those who did the exercise showed far more improvement—and the more they trained, the better they got.

The memory task differed from previous studies because, instead of learning items one by one, subjects handled auditory (consonants heard on headphones) and visual (small squares at specific locations on computer screens) stimuli presented simultaneously. They had to determine whether the current stimulus (both letter and screen position) was identical to the stimulus n items back.

In each new trial, n was increased by a value of one when subjects performed well and decreased by the same amount when they did poorly. The researchers say the demanding regimen, called n-back, engaged executive brain processes, including those that inhibit irrelevant items, monitor performance, manage two tasks simultaneously, and update memory, in addition to discouraging development of strategies and automatic responses for succeeding.

Michael Merzenich, a former neuroscientist at the University of California, San Francisco, who was not involved in the study, praised the paper but is not convinced that it demonstrates far transfer. Merzenich, chief scientific officer and co-founder of Posit Science Corporation in San Francisco, a company that develops and sells cognitive training programs, noted that the n-back test might exercise the same faculties required to perform well on standard intelligence tests. These include keeping several alternative patterns in mind and mentally rehearsing them very quickly as the task becomes increasingly complicated.

“It’s a damn good thing for a brain to be able to manipulate information with such facility in fast time,” Merzenich says. “But to say that it’s far transfer is questionable.”

Other experts are also skeptical. “It’s a little shocking to me that this would be published without any caveats,” says K. Anders Ericsson, a psychologist at Florida State University in Tallahassee who studies expert performance and memory and was also not involved in the study. “I would be one of the first to be really excited if this turned out to be a genuine reproducible effect, but the more I read, the more questions I have.” Ericsson says he is troubled by the paper’s lack of several details, among them, how the subjects and controls were recruited and how well matched they were.

Merzenich notes that the work challenges the long-standing and much-disputed idea that the core basis of intelligence is inherited and cannot be modified. “I think it’s important that someone has demonstrated,” he says, “that you can change measures of ‘intelligence’ by intensive training.”