Tense Underspecification Hypothesis
I was reading the article in which TUH is proposed: Wenzlaff, M., & Clahsen, H. (2004). Tense and agreement in German agrammatism. Brain and Language, 89(1), 57–68. http://doi.org/10.1016/S0093-934X(03)... and I found one thing confusing. Clahsen & Wenzlaff argue that tense inflection in the syntactic tree is specified for mood not tense in agrammatism. They base this on the finding that: "The materials presented to our participants all required indicative verb forms, (i.e. [+Realis]); they varied with respect to the required tense forms (as well as in terms of agreement). If [±Past] is lost and [±Realis] is preserved in agrammatism, then what should matter to the participants is that the form they choose is correct with respect to [±Realis]. Since all the forms they were offered were indicative, i.e. [+Realis], present and past-tense forms should be equally appropriate."
surely indicative would be the 'default', easiest and thus most likely unimpaired mood? Then, if the patients provide indicative in contexts where indicative is required it doesn't actually prove anything?