Limitations
weakness
REGRESSION
We acknowledge several limitations in the design and procedure, which should be considered when interpreting our results and analyses. The unexpectedly large pre-test differences forced us to split our sample by country, which led to smaller groups and reduced power compared to the study we initially conceived. Due to significant group differences at T1, we cannot rule out regression to the mean as a possible explanation for some of our effects. The analyses also tested the inclusion of a wide range of measures as covariates in a conservative, yet exploratory fashion. We highly recommend replication of our study with other cohorts of Dutch and Flemish children.An additional weakness is that we only measured reading fluency at T2. Due to an earlier pilot showing floor results and due to time constraints for testing at schools, we decided not to collect such data at T1. As a result, we could not directly test interactions between reading fluency improvement and other factors. However, by controlling reading fluency outcome for reading precursors at T1 (letter knowledge, phonological awareness, rapid automatised naming, and age), these results are nevertheless relevant and meaningful.Another issue arises from the fact that the teachers who participated were favourable, or at least open, to the use of digital tools in their classrooms, and were furthermore not blinded to the gaming conditions. Thus, they knew their treatment allocation. This may have changed their teaching style, which is difficult to control or correct for. To balance the impact single classrooms may have on intervention effects, children should ideally be randomised individually (for example, one third of a classroom playing the reading game, one third playing a control game and one third not playing). From our experience, this is hard to implement in classrooms and it would also negatively affect classroom atmosphere if some children were not allowed to play. An alternative is to implement the playing at home, which would come with its own set of challenges like how to ensure daily playing or prevent excessively long gaming sessions (Finally, the math game may not have been the best control condition. Through data collected with an auditory EEG paradigm from a subset of the children in the present study, it became apparent that playing the math game might also contribute to the development of phonological awareness skills (