Predicting errors in children’s production of verb morphology: evidence from person/number marking in Finnish and Polish
Studies of naturalistic data have suggested that young children acquiring highly-inflected languages do so in a way that is largely error-free. However, overall low error rates in children’s production may hide higher error rates in certain parts of the paradigm. To investigate this possibility, the current study elicits children’s production of person/number marking in present tense verbs in two morphologically complex languages, Finnish and Polish, which differ in the complexity of the verb inflection pattern. We investigate not only whether children make errors, but also whether input-based accounts are able to predict where in the verb paradigm errors occur.
46 native Finnish-speaking children (mean age: 50.1 months; range: 35-60) and 51 native Polish-speaking children (mean age: 46.9 months; range: 35-60) participated in the study. Children were shown animations of different characters (1st, 2nd, 3rd person; singular and plural) performing various actions, and produced both the pronoun and the inflected present-tense form of the verb. Verbs were chosen across a range of surface form frequencies and from verb classes varying in phonological neighbourhood density (PND), with counts taken from CDS corpora and standard grammar dictionaries respectively.
Analysis with mixed-effects models revealed that, for both languages, despite overall low error rates, children made more errors with verb forms with lower token frequencies in the input (Finnish: β=0.30, SE=0.11, χ²(1)=8.0, p=0.005; Polish: β=0.37, SE=0.09, χ²(1)=24.4, p<0.0001) and with verbs belonging to classes with lower PNDs (Finnish: β=0.30, SE=0.13, χ²(1)=3.78, p=0.052; Polish: β=0.078, SE=0.063, χ²(1)=4.4, p=0.037).
These findings suggest that successful models of children’s acquisition of verb morphology need to be sensitive to the statistical properties of children’s input, i.e., both token frequency (reflecting children’s retrieval of individually stored verb forms) and PND (children’s use of phonological analogy).