Slower than the remaining 2/3.
I.e. a third of folks can't or don't process input quite as quickly as the rest. I have no idea about the study apart from the blurb I heard on the radio.
Would this not be true for any study with any result, i.e., that 1/3 of the participants' results were slower (or whatever) than the other 2/3? Say, for example, that you take 99 people and have them run a 100 meter dash. 33 of them will have times slower than the other 66 -- I can guarantee it right now. In fact, they can all skip the 100 and go to the bar