To conclude, our study provides evidence that WM training
targeting multiple functional categories is less efficient
than WM training focusing on single processes only. Given
that transfer effects of WM training are generally rather
small (if they are observed at all), our results suggest that
future training interventions (at least those that extend only four weeks) should better focus on specific functional categories
in order to enhance the probability of observing
transfer. The magnitude of training effects was not modulated
by age; transfer was, however, very narrow for both
age groups.