Effect of subject types on the production of auxiliary is in young English-speaking children.
OBJECTIVE
In this study, the authors tested the unique checking constraint (UCC) hypothesis and the usage-based approach concerning why young children variably use tense and agreement morphemes in obligatory contexts by examining the effect of subject types on the production of auxiliary is.


METHODS
Twenty typically developing 3-year-olds were included in this study. The children's production of auxiliary is was elicited in sentences with pronominal subjects, high-frequency lexical noun phrase (NP) subjects (e.g., the dog), and low-frequency lexical NP subjects (e.g., the deer).


RESULTS
As a group, children did not use auxiliary is more accurately with pronominal subjects than with lexical NP subjects. Furthermore, individual data revealed that although some children used auxiliary is more accurately with pronominal subjects than with lexical NP subjects, the majority of children did not show this trend.


CONCLUSIONS
The symmetry observed between lexical and pronominal subjects supports the predictions of the UCC hypothesis, although additional mechanisms may be needed to account for the asymmetry between subject types in some individual children. Discrepant results between the present study and previous studies were attributed to differences in task formats and children's developmental levels.
Guo
Ling-Yu
LY
who is now with the Department of Communicative Disorders and Sciences, University at Buffalo-The State University of New York, 118 Cary Hall, Buffalo, NY 14214, USA. lingyugu@buffalo.edu
Owen
Amanda J
AJ
Tomblin
J Bruce
JB
D002663:Child Language; D002675:Child, Preschool; D005260:Female; D006801:Humans; D007802:Language; D007804:Language Development; D007807:Language Tests; D016015:Logistic Models; D008297:Male; D008954:Models, Biological; D012660:Semantics; D014825:Vocabulary