There is a mounting body of evidence that student self-explanation and contentful talk in humanhuman tutorial dialogue are correlated with increased learning gain (Chi et al., 1994;Purandare and Litman, 2008;.
computer tutors that understand student explanations have the potential to improve student learning (Graesser et al., 1999;Jordan et al., 2006;Aleven et al., 2001;Dzikovska et al., 2008).