Treatment of sentence production in German agrammatism: a multiple single case study

Individuals with agrammatism have specific problems with the production of movement-derived non-canonical sentence structures which, according to the Tree Pruning Hypothesis (TPH, Friedmann & Grodzinsky, 1997; Friedmann, 2001), are due to an inability to access hierarchically higher nodes of the syntactic tree. Thus, movement-derived structures relying on higher nodes in the syntactic tree cannot be produced correctly. With respect to treatment outcome, the TPH predicts that a specific remediation of structures relying on higher nodes should lead to an improvement of all syntactic abilities and across different sentence types, relying on lower node structures though no specific treatment has focussed on lower node structures. This has been observed by Friedmann et al. (2000) in a Hebrew-speaking agrammatic patient. Alternatively, the complexity account of treatment efficacy (CATE, Thompson et al., 2003) predicts that remediation of syntactically complex sentences results in an improvement of syntactically less complex sentences but not inversely. The authors reported generalization effects from production of sentences in which movement occurs within an embedded clause (syntactically complex sentences, i.e. object-relative-clauses) to sentences in which movement occurs in the matrix clause (simple sentences, i.e. object extracted who-questions). As syntactically complex sentences rely on higher node structures than less complex sentences, both accounts predict generalization effects in the same direction after treatment. In sum TPH and CATE both, postulate that treatment of complex, respectively hierarchically higher represented structures result in improved production of syntactically simpler, respectively hierarchically lower represented sentences structures. Inversely, treating simple or lower represented sentences does not lead to an improvement in the production of complex, higher represented sentences. However, Thompson and colleagues postulate generalization effects only within structures that rely on the same movement operations (i.e. wh-movement or NPmovement) as the treated structures. After treatment of structures relying on wh-movement (i.e. object-relative-clauses), Thompson et al. (1997) observed an improvement only in the production of other wh-movement structures (i.e. wh-questions) but not of NP-movement structures (i.e. subject-raising, passive-sentences) and vice versa.