“…That is, in the studies comparing percentage mastery versus fast rate mastery, inevitably the participants who received rate instruction also received more instructional presentations. Recently, investigators have isolated the instructional unit that predicts learning, the learn unit (Albers & Greer, 1991 ;Emurian, Hu, Wang , & Durham , 2000;Emu rian , 2004;Greer & McDonough, 1999;Greer, McCorkle, & Williams, 1989;Ingham & Greer, 1992;Selinske, Greer, & Lodhi , 1991). A learn unit includes the teacher or automated teaching device ensuring the student's attention, the unambiguous delivery of an antecedent that is to be the discriminative stimulus when the student has mastered the discriminated operant, and delivery of either a reinforcer or a correction .…”