"For the study, Prof Ullen and Guy Madison, from Sweden's Umea University, asked 34
right-handed men aged between 19 and 49 to tap a drumstick at a variety of different intervals."
ah. so it's the
left-handed drummers that are the stupid ones.

and this reader comment says it all:
Yes I was a drummer, and multitasking with four limbs can be difficult, especially one in 4/3 time and the other hand in 4/4.
maybe there's something to this 'dumb and drummer' thing after all. [I keed, I keed!]