Last June I posted a blog entry about training working memory, focusing on a study by Tom Redick and his colleagues, which concluded that training working memory might boost performance on whatever task was practiced, but it would not improve fluid intelligence.
(Measures of fluid intelligence are highly correlated with measures of working memory, and improving intelligence would be most people's purpose in undergoing working memory training.)
I recently received an email from Martin Walker, of MindSparke.com, which offers brain training. Walker sent me a polite email arguing that the study is not ecologically valid: that is, the conclusions may be accurate for the conditions used in the study, but the conditions used in the study do not match those typically encountered outside the laboratory. Here's the critical text of his email, reprinted with his permission:
"There is a significant problem with the design of the study that invalidates all of the hard work of the researchers--training frequency. The paper states that the average participant completed his or her training in 46 days. This is an average frequency of about 3 sessions per week. In our experience this frequency is insufficient. The original Jaeggi study enforced a training frequency of 5 days per week. We recommend at least 4 or 5 days per week.
With the participants taking an average of 46 days to complete the training, the majority of the participants did not train with sufficient frequency to achieve transfer. The standard deviation was 13.7 days which indicates that about 80% of the trainees trained less frequently than necessary. What’s more, the training load was further diluted by forcing each session to start at n=1 (for the first four sessions) or n=2, rather than starting where the trainee last left off."
I forwarded the email to Tom Redick, who replied:
"Your comment about the frequency of training was something that, if not in the final version of the manuscript, was questioned during the review process. Perhaps it would’ve been better to have all subjects complete all 20 training sessions (plus the mid-test transfer session) within a shorter prescribed amount of time, which would have led to the frequency of training sessions being increased per week. Logistically, having subjects from off-campus come participate complicated matters, but we did that in an effort to ensure that our sample of young adults was broader in cognitive ability than other cognitive training studies that I’ve seen. This was particularly important given that our funding came from the Office of Naval Research – having all high-ability 18-22 year old Georgia Tech students would not be particularly informative for the application of dual n-back training to enlisted recruits in the Army and Marines.
However, I don’t really know of literature that indicates the frequency of training sessions is a moderating factor of the efficacy of cognitive training, especially in regard to dual n-back training. If you know of studies that indicate 4-5 days per week is more effective than 2-3 days week, I’d be interested in looking at it.
As mentioned in our article, the Anguera et al. (2012) article that did not include the matrix reasoning data reported in the technical report by Seidler et al. (2010) did not find transfer from dual n-back training to either BOMAT or RAPM [Bochumer Matrices Test and Raven's Advanced Progressive Matrices, both measures of fluid intelligence], despite the fact that “Participants came into the lab 4–5 days per week (average = 4.5 days) for approximately 25 min of training per session” (Anguera et al., 2012), for a minimum of 22 training sessions. In addition, Chooi and Thompson (2012) administered dual n-back to participants for either 8 or 20 days, and “Participants trained once a day (for about 30 min), four days a week”. They found no transfer to a battery of gF and gC tests, including RAPM.
In our data, I correlated the amount of dual n-back practice gain (using the same method as Jaeggi et al) during training and the number of days it took to finish all 20 practice sessions (and 1 mid-test session). I would never really trust a correlation of N = 24 subjects, but the correlation was r = -.05.'.
I re-analyzed our data, looking only at those dual n-back and visual search training subjects that completed the 20 training and 1 mid-test session within 23-43 days, meaning they did an average of at least 3 sessions of training per week. For the 8 gF tasks (the only ones I analyzed), there was no hint of an interaction or pattern suggesting transfer from dual n-back.
So to boil Redick's response down to a sentence, he's pointing out that other studies have observed no impact on intelligence when using a training regimen closer to that advocated by Walker, and Redick finds no such effect in a follow-up analysis of his own data (although I'm betting he would acknowledge that the experiment was not designed to address this question, and so does not offer the most powerful means of addressing it.)
So it does not seem that training frequency is crucial.
A final note: Walker commented in another email that customers of MindSparke consistently feel that the training helps, and Redick remarked that subjects in his experiments have the same impression. It just doesn't bear out in performance.
(Measures of fluid intelligence are highly correlated with measures of working memory, and improving intelligence would be most people's purpose in undergoing working memory training.)
I recently received an email from Martin Walker, of MindSparke.com, which offers brain training. Walker sent me a polite email arguing that the study is not ecologically valid: that is, the conclusions may be accurate for the conditions used in the study, but the conditions used in the study do not match those typically encountered outside the laboratory. Here's the critical text of his email, reprinted with his permission:
"There is a significant problem with the design of the study that invalidates all of the hard work of the researchers--training frequency. The paper states that the average participant completed his or her training in 46 days. This is an average frequency of about 3 sessions per week. In our experience this frequency is insufficient. The original Jaeggi study enforced a training frequency of 5 days per week. We recommend at least 4 or 5 days per week.
With the participants taking an average of 46 days to complete the training, the majority of the participants did not train with sufficient frequency to achieve transfer. The standard deviation was 13.7 days which indicates that about 80% of the trainees trained less frequently than necessary. What’s more, the training load was further diluted by forcing each session to start at n=1 (for the first four sessions) or n=2, rather than starting where the trainee last left off."
I forwarded the email to Tom Redick, who replied:
"Your comment about the frequency of training was something that, if not in the final version of the manuscript, was questioned during the review process. Perhaps it would’ve been better to have all subjects complete all 20 training sessions (plus the mid-test transfer session) within a shorter prescribed amount of time, which would have led to the frequency of training sessions being increased per week. Logistically, having subjects from off-campus come participate complicated matters, but we did that in an effort to ensure that our sample of young adults was broader in cognitive ability than other cognitive training studies that I’ve seen. This was particularly important given that our funding came from the Office of Naval Research – having all high-ability 18-22 year old Georgia Tech students would not be particularly informative for the application of dual n-back training to enlisted recruits in the Army and Marines.
However, I don’t really know of literature that indicates the frequency of training sessions is a moderating factor of the efficacy of cognitive training, especially in regard to dual n-back training. If you know of studies that indicate 4-5 days per week is more effective than 2-3 days week, I’d be interested in looking at it.
As mentioned in our article, the Anguera et al. (2012) article that did not include the matrix reasoning data reported in the technical report by Seidler et al. (2010) did not find transfer from dual n-back training to either BOMAT or RAPM [Bochumer Matrices Test and Raven's Advanced Progressive Matrices, both measures of fluid intelligence], despite the fact that “Participants came into the lab 4–5 days per week (average = 4.5 days) for approximately 25 min of training per session” (Anguera et al., 2012), for a minimum of 22 training sessions. In addition, Chooi and Thompson (2012) administered dual n-back to participants for either 8 or 20 days, and “Participants trained once a day (for about 30 min), four days a week”. They found no transfer to a battery of gF and gC tests, including RAPM.
In our data, I correlated the amount of dual n-back practice gain (using the same method as Jaeggi et al) during training and the number of days it took to finish all 20 practice sessions (and 1 mid-test session). I would never really trust a correlation of N = 24 subjects, but the correlation was r = -.05.'.
I re-analyzed our data, looking only at those dual n-back and visual search training subjects that completed the 20 training and 1 mid-test session within 23-43 days, meaning they did an average of at least 3 sessions of training per week. For the 8 gF tasks (the only ones I analyzed), there was no hint of an interaction or pattern suggesting transfer from dual n-back.
So to boil Redick's response down to a sentence, he's pointing out that other studies have observed no impact on intelligence when using a training regimen closer to that advocated by Walker, and Redick finds no such effect in a follow-up analysis of his own data (although I'm betting he would acknowledge that the experiment was not designed to address this question, and so does not offer the most powerful means of addressing it.)
So it does not seem that training frequency is crucial.
A final note: Walker commented in another email that customers of MindSparke consistently feel that the training helps, and Redick remarked that subjects in his experiments have the same impression. It just doesn't bear out in performance.
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