Increasing Working Memory Makes Even Adults Smarter

I have pointed out a study in an earlier post a study that showed the IQ of children around age six can be increased by training them to increase their working memory capacity. This ability of working memory training to improve intelligence has now been demonstrated in young adults (mean age = 25.6 years). Subjects were trained on a so-called dual n-back test in which subjects were asked to recall a visual stimulus that they saw two, three or more stimulus presentations in the past. The task was dual in the sense that two stimuli were presented simultaneously for a half second, followed by a 2.5 second delay until the next stimulus. One stimulus type was a square in which another smaller square was shown in one of eight possible positions within the larger square. At the same time one of eight consonants were presented through headphones. A response was required every time one of the presented stimuli matched the one that had been presented n positions back in the sequence. As performance improved with each block of trials, the task demands were increased my shifting from two-back to three, then three to four, etc. Daily training took about 25 minutes.

Intelligence tests were periodically given that were based on visual analogy problems of increasing difficulty. Each problem presented a matrix of patterns in which one pattern was missing. The task was to select the missing pattern among a set of given response alternatives. This kind of testing measures what is called "fluid" intelligence, which refers to the ability to reason and solve new problems independently of previously acquired knowledge. What the investigators found was that working memory training improved scores on the intelligence test. Moreover, the effect was dose-dependent, in that intelligence scores increased in a steady straight-line fashion as the number of training sessions increased from 8 to 12 to 17 to 19. Working memory capacity presumably transfers to visual analogy tasks because you have to hold many visual features in working memory while you try to identify which pattern is missing in the matrix.

These results also challenge a widely held view that intelligence becomes fixed at a young age and cannot be increased by experience.

Source: Jaeggi, S. M. et al. 2008. Improving fluid intelligence with training on working memory. Proc. Natl. Acad. Science. www.pnas.org/cgi/doi/10.1073/pnas.0801268105