Effects of a Complexity-Based Approach on Generalization of Past Tense -ed and Related Morphemes

Purpose: In a previous article, we reported that beginning treatment for regular past tense -ed with certain types of verbs led to greater generalization in children with developmental language disorder than beginning treatment with other types of verbs. This article provides updated data from that study, including the addition of data from 3 children, results from naturalistic language samples, and data from a third time point. Method: Twenty 4-to 9-year-old children with developmental language disorder (10 per condition) were randomly assigned to receive language intervention in which the verbs used to teach regular past tense -ed were manipulated. Half received easy first intervention, beginning with highly frequent, telic, phonologically simple verbs, and half received hard first intervention, beginning with less frequent, atelic, and phonologically complex verbs. The design used a train-tocriterion approach, with children receiving up to 36 visits. Performance was assessed using elicited production probes and language samples before intervention, immediately following intervention and 6-8 weeks later. Results: Children in the hard first group showed greater gains on the use of regular past tense -ed in both structured probes (at immediate post only) and in language samples (at both immediate and delayed post). Gains attributable to therapy were not observed in untreated morphemes. Conclusions: This study suggests that the choice of therapy materials, with an eye on the role that treatment stimuli play in generalization, is important for treatment efficacy. Clinicians should consider early selection of atelic, lower-frequency, phonologically complex verbs when teaching children to use regular past tense -ed. Further work expanding this to other morphemes and a larger population is needed to confirm this finding.