Wow, is this for real? My DS8, that many would love to call ADHD officially (and I go back and forth all the time as to whether he or is not), did this finger tapping exercise and had NO mirror movement at all. I looked in his OT records and the same test was given to him during his OT eval last year and it is noted that there were no associated mirror movements. So interesting!
Oh boy, my youngest (age 4) did indeed have the mirror movements! But he seems very, very non-adhd (has the executive functioning skills of a 30 year old)!
ETA: oh, I just realized they said all kids under 5 or so will have the involuntary mirror movements - so I guess it's just his age!