Complexity and cross-linguistic transfer in intervention for Spanish-English bilingual children with speech sound disorder.

With bilingual children, intervention for speech sound disorders must consider both of the child's phonological systems, which are known to interact with each other in development. Further, cross-linguistic generalization following intervention for bilingual children with speech sound disorders (i.e., the impact of treatment in one language on the other) has been documented to varying degrees in some prior studies. However, none to date have documented the cross-linguistic impact of treatment with complex targets (e.g., consonant clusters) for bilingual children. Because complex phonological targets have been shown to induce system-wide generalization within a single language, the potential for bilingual children to generalize learning across languages could impact the efficiency of intervention in this population. This pilot intervention study examines the system-wide, cross-linguistic effects of treatment targeting consonant clusters in Spanish for two Spanish-English bilingual children with phonological disorder. Treatment was provided with 45-minute sessions in Spanish via teletherapy, three times per week for six weeks. Comprehensive phonological probes were administered in English and Spanish prior to intervention and across multiple baselines. Pre-intervention data were compared to data from probes administered during and after intervention to generate qualitative and quantitative measures of treatment outcomes and cross-linguistic generalization. Results indicate a medium effect size for system-wide generalization in Spanish (the language of treatment) and English (not targeted in treatment), for both participants (mean effect size in Spanish: 3.6; English 4.3). These findings have implications for across-language transfer and system-wide generalization in treatment for bilingual children.