A beneficial effect of a Cogmed working memory training on intelligence without an improvement in working memory capacity

A Cogmed working memory training was done aimed to enhance intelligence in a group of adolescents at risk for school dropout and with below average IQ through an increase in working memory capacity. The adolescents came from poor families and 84% came from minority groups. The effect of the Cogmed working memory training was tested in a randomized control trial with a reading comprehension and a no-training control group. We took care that the amount of coaching to ensure treatment integrity was similar in both training groups. The trainings took five weeks but were followed two months later by a 1-week booster. Participants were 64 students (42 boys and 22 girls) with a mean age of 14,6 years (SD = 16.5 months). An intermediate-test was done after the 5 week training and a posttest at the end of the year, 3 months after the booster. Measures of working memory capacity were involved at pre-, intermediate and posttest. IQ and school achievement were included at pretest and posttest. We found short but no long-term effects on working memory capacity. Surprisingly, at posttest both trainings had an effect on IQ and school achievement in the absence of an increase in working memory capacity. We argue that these results might be due to more general aspects of these interventions, in particular the coaching and support that were provided to the students.