Training duration
To ensure that the effect of the intervention between control and experimental group were not biased by how long participants trained, we ensured that there was only a small difference (Cohen’s d < 0.4) between the average total playtimes between each group. In the case of a large difference (d ≥ 0.4), we excluded the participants with the most extreme values until the maximum threshold is reached. This positive control was added after we modified the training length recommendation; this modification received editorial approval before the beginning of data collection.