Question 2: participant characteristics
handedness, reading difficulties, dyslexia
To answer the second research question whether certain subgroups of children benefit more from GraphoGame-NL exposure than others, we looked for possible interaction effects of gaming condition with pre-test scores, age, binary sex, familial risk for dyslexia, abstract reasoning, and home language environment, on the above-presented response-to-intervention variables. In almost all analyses, participant characteristics explained unique variance as covariates and thus helped to describe more robust and generalisable intervention effects. However, we did not find statistically significant interaction effects between participant characteristics and gaming condition, indicating that there were no participant characteristics that modulated response specifically to GraphoGame-NL intervention.Familial risk for dyslexia was assessed by parental questionnaires inquiring about the occurrence of reading difficulties in first degree relatives. According to the stepwise model building, familial risk was a relevant predictor for PROEF phonological awareness scores at T2 in the Belgian sample, reflected in slightly lower scores for children with a familial risk for dyslexia across all gaming conditions (Age was a relevant covariate in analyses of in-game response times of timed letter-sound identification (Sex was a relevant covariate for letter-sound identification accuracy in the Dutch sample at both testing points (Nonverbal intelligence, as measured by the SON-R 6-40, was a relevant covariate for the CELF phonological awareness at T2 in the Belgian sample (Home language environment and handedness were never relevant predictors.