approximately 25 minutes per day for between 8 and 19 days had significantly greater pre-to-posttest increases in their scores on a matrix test of fluid intelligence. There was no long-term follow-up to assess how enduring the effects of training were. Two later n-back studies did not support the findings of Jaeggi et al. Although participants' performance on the training task improved, these studies showed no significant improvement in the mental abilities tested, especially fluid intelligence and working memory capacity. Thus the balance of findings suggests that training for the purpose of increasing working memory can have specific short-term effects but no effects on gf. See also 21st century skills CHC theory Deeper learning General intelligence factor Intelligence John L. Horn Malleability of intelligence Nootropic Outline of human intelligence Psychometrics Raymond Cattell Spatial intelligence (psychology) Three-stratum theory References Intelligence by type