Disentangling Bilingualism and Developmental Language Disorder in the Acquisition of Spanish Verbal Agreement Morphology.
Patrick D Thane, Anny P Castilla-Earls, Ana T Pérez-Leroux and 1 others
Typical children produced more correct verb endings than children with DLD, in both bilingual and monolingual groups.
But the errors they made looked the same across all four groups, so the type of error won't help you tell DLD from typical bilingual development.
Key findings
1Children with typical development produced more target-like preterit verbal agreement than children with DLD, in both the bilingual and the monolingual groups.
2Typical bilingual children and typical monolingual children did not differ significantly in their production of target-like verbal agreement, arguing against a strong bilingualism effect on this structure in the age range tested.
3The patterns of non-target responses — whether children overused third-person forms or produced bare, uninflected verbs — did not differ significantly between children with DLD and TD, nor between bilinguals and monolinguals, so error type does not serve as a qualitative marker of DLD.
Still to come
How it was doneWhat they foundWhat it means for SLPs
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What it does not show
Cross-sectional design: each child was tested once, so the authors cannot say whether the differences they see reflect a developmental trajectory or a stable group difference. Group-level analysis only: the authors acknowledge that individual variation in Spanish exposure, schooling, and home language use was not modelled, and that a typical bilingual child with low exposure can score in the same range as a child with DLD. Elicited production only: the task was a booklet-based prompt, not spontaneous speech or a receptive task. The authors note that elicited production may yield lower accuracy than spontaneous samples, and that a receptive forced-choice task would add information. Overlap between groups: the individual-level scatter plot shows that the four groups overlap between 40% and 60% target-like production up to 75 months of age, so group membership is not a clean diagnostic boundary. The bilingual sample includes children from two very different sociolinguistic environments (upstate New York with minimal Spanish community presence vs. Houston with dual-language schools), and the authors did not model this variable.
Declared interests
Funded by the National Institute on Deafness and Other Communication Disorders (a US government agency). No industry sponsor, no author disclosures of financial ties to a commercial product or assessment tool are reported.
The easy way to misread this
Do not read the null bilingualism finding (typical bilinguals and monolinguals did not differ) as evidence that bilingualism has no effect on Spanish verb morphology. The sample included children from two very different language environments, the task was elicited rather than spontaneous, and the authors themselves note that a typical bilingual child with low Spanish exposure can score in the same range as a child with DLD. The null result means this particular structure, in this age range, in this sample, did not separate the two groups. It does not rule out bilingualism effects on other structures or in other contexts.
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