To deter­mine if some­thing works we first need to define what we mean by “work”. A machine to train abdom­i­nal mus­cles prob­a­bly won’t “work” if what we mea­sure is blood pres­sure. In the same way, a pro­gram train­ing audi­to­ry pro­cess­ing speed may not work if visu­al func­tions are mea­sured (see Chap­ter 1 for a bet­ter…