A key research report on working memory was summarized in a recent guest column in the New York Times by Sam Wang and Sandra Aamodt. Below is a summary of what they said in the article:
J. R. Flynn first noted that standardized intelligence quotient (I.Q.) scores were rising by three points per decade in many countries, and even faster in some countries like the Netherlands and Israel. For instance, in verbal and performance I.Q., an average Dutch 14-year-old in 1982 scored 20 points higher than the average person of the same age in his parents’ generation in 1952. These I.Q. increases over a single generation suggest that the environmental conditions for developing brains have become more favorable in some way.
What might be changing? One strong candidate is working memory, defined as the ability to hold information in mind while manipulating it to achieve a cognitive goal. Examples include remembering a clause while figuring out how it relates the rest of a sentence, or keeping track of the solutions you’ve already tried while solving a puzzle. Flynn has pointed out that modern times have increasingly rewarded complex and abstract reasoning. Differences in working memory capacity account for 50 to 70 percent of individual differences in fluid intelligence (abstract reasoning ability) in various meta-analyses, suggesting that it is one of the major building blocks of I.Q. (2-4). This idea is intriguing because working memory can be improved by training.
A common way to measure working memory is called the "n-back" task. Presented with a sequential series of items, the person taking the test has to report when the current item is identical to the item that was presented a certain number (n) of items ago in the series. For example, the test taker might see a sequence of letters like
L K L R K H H N T T N X
presented one at a time. If the test is an easy 1-back task, she should press a button when she sees the second H and the second T. For a 3-back task, the right answers are K and N, since they are identical to items three places before them in the list. Most people find the 3-back condition to be challenging.
A recent paper reported (5) that training on a particularly fiendish version of the n-back task improves I.Q. scores. Instead of seeing a single series of items like the one above, test-takers saw two different sequences, one of single letters and one of spatial locations. They had to report n-back repetitions of both letters and locations, a task that required them to simultaneously keep track of both sequences. As the trainees got better, n was increased to make the task harder. If their performance dropped, the task was made easier until they recovered.
Each day, test-takers trained for 25 minutes. On the first day, the average participant could handle the 3-back condition. By the 19th day, average performance reached the 5-back level, and participants showed a four-point gain in their I.Q. scores.
The I.Q. improvement was larger in people who’d had more days of practice, suggesting that the effect was a direct result of training. People benefited across the board, regardless of their starting levels of working memory or I.Q. scores (though the results hint that those with lower I.Q.s may have shown larger gains). Simply practicing an I.Q. test can lead to some improvement on the test (6), but control subjects who took the same two I.Q. tests without training improved only slightly.
Since the gains accumulated over a period of weeks, training is likely to have drawn upon brain mechanisms for learning that can potentially outlast the training. But this is not certain. If continual practice is necessary to maintain I.Q. gains, then this finding looks like a laboratory curiosity. But if the gains last for months (or longer), working memory training may become as popular as and more effective than games like sudoku among people who worry about maintaining their cognitive abilities.
Now, some caveats. The results, though tantalizing, are not perfect. It would have been better to give the control group some other training not related to working memory, to show that the hard work of training did not simply motivate the experimental group to try harder on the second I.Q. test. The researchers did not test whether working memory training improved problem-solving tasks of the type that might occur in real life. Finally, they did not explore how much improvement would be seen with further training.
Sources:
1. Flynn, J. R. 1987. Massive IQ gains in 14 nations: What IQ tests really measure. Psych. Bull. 101 (2) 171-191.
2. P.L. Ackerman (1987) Individual differences in skill learning: An integration of psychometric and information processing perspectives. Psychological Bulletin 102:3–27.
3. M.J. Kane, D.Z. Hambrick, and A.R.A. Conway (2005) Working memory capacity and fluid intelligence are strongly related constructs: comment on Ackerman, Beier, and Boyle (2005). Psychological Bulletin 131:66–71.
4. H.-M. Süss, K. Oberauer, W.W. Wittmann, O. Wilhelm, and R. Schulze (2002) Working-memory capacity explains reasoning ability—and a little bit more. Intelligence 30:261–288.
5. S.M. Jaeggi, M. Buschkuehl, J. Jonides, and W.J. Perrig (2008) Improving fluid intelligence with training on working memory. Proceedings of the National Academy of Sciences USA 105:6829-6833.
6. D.A. Bors, F. Vigneau (2003) The effect of practice on Raven’s Advanced Progressive Matrices. Learning and Individual Differences 13:291–312.
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