How non-native are natives? Individual differences in the oral narratives of adult native speakers of Brazilian Portuguese with different levels of schooling

As a test of the uniformity of competence assumption—the notion that there is an ideal state of native speaker competence—and to establish how variability in native speakers compares to variability in non-native speakers, this study examined individual differences in morphosyntactic attainment in adult monolingual native speakers of Brazilian Portuguese. Using an oral narrative task, we analyzed global lexical and syntactic properties of the speech produced as well as morphosyntactic properties of Brazilian Portuguese that differ by register, like plural agreement, and gender in noun phrases, a property that is typically difficult to acquire in second language and bilingual acquisition. Seventy-one adult native speakers of Brazilian Portuguese with different levels of education (low, mid, high) were the experimental groups and 23 educated non-native speakers of intermediate proficiency in Portuguese were the control group. Results indicated differences among the native speakers in overall fluency, lexical and syntactic complexity related to level of education but few differences between the low education native speakers and the non-native speakers. The morphosyntactic analysis of gender and number mismatches, however, confirmed difficulties with gender agreement and different number mismatches patterns for non-native speakers compared to the low educated native speakers, whose plural mismatches reflected the typical spoken language variability attested in the language. We discuss how literacy experience contributes to different aspects of linguistic competence in native and non-native speakers.