Visual perception of speed in drivers with ADHD

Effects of ADHD on driving speed were studied in a driving simulator with only visual motion cues, by comparing drivers with ADHD diagnosis (n = 36) to drivers from a normal student population (n = 28). Their task was to repeatedly accelerate to own preferred speed for a total of 26 trials (2 baseline, 24 experimental trials). Field of view (1, 3, 5, and 7 monitors) and virtual road markings (on, off) were manipulated. These eight experimental conditions were presented three times each (replicates). Overall mean speed did not differ between groups, but the ADHD group was less affected by the extra motion cues. Also, whereas the control group lowered their speed between replicates, the ADHD group did not. The combined results suggest that for ADHD drivers, speed perception is more of a rule-based skill and more based on attention, whereas the normal student population perceives speed more effortlessly.