Complexity in treatment of syntactic deficits.

PURPOSE This article addresses complexity in the context of treatment for sentence structural impairments in agrammatic aphasia, with emphasis on noncanonical sentences involving linguistic movement and their related counterparts. Extensions of the complexity effect to recovery of canonical sentences also are discussed, stressing the linguistic properties of verbs as well as grammatical morphology in building complexity hierarchies. METHOD A number of variables to consider in developing complexity hierarchies in the syntactic domain are addressed, and a series of studies using single-subject controlled experimental analysis are discussed. RESULTS Findings across studies show that training complex sentences results in improvement of simpler structures when, and only when, the underlying linguistic properties are shared by both. The opposite approach, training simple structures first and building to more complex ones, does not provide the full benefit of treatment, in that little or no generalization occurs across structures. CONCLUSION Using complex language material as a starting point for treatment of sentence structural deficits in aphasia results in cascading generalization to simpler, linguistically related material and expands spontaneous language production in many language-disordered adults with aphasia. Clinicians are, therefore, urged to adopt this approach in clinical practice, even though it is counterintuitive and departs significantly from conventional treatment methods.