Procedure
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The participants were consecutively divided on a random basis into two groups, the IR-MPH first group (MPH/placebo group) and the placebo first group (placebo/MPH group). All adults participated on two trial days, with a washout period of 4 days in-between. Upon arrival on the first and second trial day, it was checked for alcohol (ETG 300® Rapid Urine Test Panel; Alcometer Lion 500®—Breath alcohol test) and drug use (Multi-Drug 15 Drugs Rapid Urine Test Panel; ZOP 50® Urine Test Panel; RightSign® Urine). Females were screened for pregnancy (Clearblue®) on the first trial day. Two baselines, one for each trial day, were used to ensure current baseline values and accurately measure the difference between baselines and pills. In one session, the adults received IR-MPH (one single-dose Medikinet® 20 mg Immediate Release pill, first-hand choice of dose during drug trials at the clinic) and in the other session they received placebo (one single-dose placebo). IR-MPH and placebo were counterbalanced across subjects. The study design is shown in Fig. Flowchart of the procedure and randomization of the study. MPH= Methylphenidate, Each session started with a baseline QbTest (without any pill or medication). The adults were shown an instruction video of the QbTest and received additional oral instructions. They were asked to put on the headband and to sit comfortably while holding the response button in their dominant hand and relaxing the other hand on their lap. A practice QbTest trial was given to check if the participant understood the task. Then the adult did the full 20-min QbTest. After the baseline QbTest the adult was given the pill. Eighty minutes elapsed between the adult orally ingesting the pill and began the 2