I'm probably just being overly critical here but his example of "deciding if a number is odd or even in a matter of seconds" seems odd, I think 2nd graders and up can tell you in half a second or less whether or not a number's even or odd.
He says:
"In addition to working memory, researchers are seeking to improve fluid intelligence by training other basic mental skills — perceptual speed (deciding, in a matter of seconds, whether a number is odd or even), visual tracking (on a shoot-’em-up computer game, for instance) or quickly switching between a variety of tasks."