Well, I was going through some old magazines and Parenting had a great article back in April 2012 (I know... I'm behind on everything... even reading magazines) that spoke on this topic. The article focused on the speed of cartoons and its effects on their attention span. They had three groups of kids: those who watched a fast paced cartoon, those who watched a slower paced cartoon, and those who did not watch TV at all and drew instead. They stated, "the kids who viewed the faster-paced bug-eyed yellow square did not perform as well as the scribblers and those who watched the mellow tot."
Next time your child is watching a cartoon or kid-friendly show, take notice of how fast the characters are moving, the number of scene changes (and the speed at which it happens), if the camera is panning back and forth between characters or has a wider angle so that there is less movement, etc.