Effects of linguistic and usage-based factors on children's acquisition of English derivational morphology

Children must learn the variation in morphological productivity based on limited inputs. Previous studies have suggested several factors in the acquisition of derivational morphology. Some scholars have focused on semantic and phonological transparency, whereas others emphasize the role of input frequency. This paper explores the factors that influence children's acquisition and use of English derivational morphology. For this, we analyzed children's production of derived words in a million-word corpus taken from the CHILDES database. The data came from the voluntary production of derived words by 469 individuals at age 3-10. We extracted 7,234 derived words that were instances of 704 derivative types from the corpus, and conducted multiple regression analyses by using Baayen's (1993) hapax-conditioned degree of productivity as a function of several linguistic and usage-based factors. The results indicate that the family frequency of an affix in the input plays the most important role in the regression model, and that semantic and phonological transparency has only limited effects on the total variation. In particular, we discuss how a single principle can explain children's performance on derivational morphology at all ages, and how our new conception of continuity supports the view that language development should be constrained by both linguistic and usage-based factors.