Statistical analysis
Medication and placebo efficacy were tested by calculating the differences which we define as the delta scores. Repeated measures ANOVA were used for testing differences in raw test scores between the four conditions (baseline-pre IR-MPH, post IR-MPH, baseline-pre placebo, post placebo) as within-subject factors and calculating changes in performance in the three five-minute Quartiles Q2, Q3 and Q4. Degrees of freedom were corrected according to Greenhouse & Geisser. Bonferroni correction was used for post-hoc comparisons of means. One-way ANOVA was used to analyse differences between groups and gender. Cohen´s d was calculated for effect sizes. Cohen´s d = 0.20 was considered a small effect, d = 0.50 a medium effect and d = 0.80 a large effect. The test–retest reliability between the two baseline conditions (baseline 1