Sequence and system in the acquisition of tense and agreement.
OBJECTIVE
The relatedness of tense morphemes in the language of children younger than 3 years of age is a matter of controversy. Generativist accounts predict that the morphemes will be related, whereas usage-based accounts predict the absence of relationships. This study focused on the increasing productivity of the 5 morphemes in the tense productivity score (copula BE, third-person singular present -  3s, past -  ed, auxiliary DO, auxiliary BE;   Hadley & Short, 2005) and their relationship to one another.


METHODS
Twenty typically developing children were observed longitudinally from 21 to 33 months of age. One hour of naturalistic caregiver-child interaction sampled every 3 months was analyzed.


RESULTS
Copula BE was more productive than all other morphemes from age 27 months onward. Auxiliary BE was significantly less productive than -  3s, -  ed, and DO from age 27 months onward. Evaluation of third-person singular tense morphemes at age 33 months revealed that the productivity scores of copula   is, -  3s, and   does were all correlated.


CONCLUSIONS
There is sequence and simultaneity in development that no prior framework has fully explained, as well as evidence of cross-morpheme relationships. In this article, the authors interpret these findings as support for the gradual morphosyntactic learning hypothesis (  Rispoli & Hadley, 2011;   Rispoli, Hadley, & Holt, 2009).
University of Illinois at Urbana-Champaign, IL, USA. mrispoli@illinois.edu
Matthew
M
Rispoli
Pamela A
PA
Hadley
Janet K
JK
Holt
D002663:Child Language; D002675:Child, Preschool; D005260:Female; D006801:Humans; D007223:Infant; D007804:Language Development; D007807:Language Tests; D008137:Longitudinal Studies; D008297:Male; D012660:Semantics; D013060:Speech; D013068:Speech Production Measurement; D014705:Verbal Behavior