First things third? The extension of canonically third-person singular inflections to first-person singular subjects in adult heritage Spanish

Abstract Previous research has found that heritage speakers of Spanish sometimes extend canonically third-person singular (3PS) verbal morphology to first-person singular (1PS) subjects, a pattern that has been reported with both children and adults across a variety of different verbal paradigms (e.g., preterite). However, despite clear evidence of 3PS extensions in heritage Spanish, no previous research has systematically investigated the factors that shape this common, yet still poorly understood morphological tendency. To test whether heritage speakers’ likelihood of extending 3PS forms is shaped by paradigmatic frequency, the present study investigated adult heritage speakers’ production and comprehension of person agreement in the present perfect paradigm, which is relatively low frequency in Latin American/US varieties of Spanish, and the preterite paradigm, which is relatively much more frequent. 30 adult heritage speakers of Latin American/US Spanish completed two oral production tasks and one listening comprehension task, all of which targeted their knowledge of 1PS and 3PS morphology in both the present perfect and preterite paradigms. Results of the production experiments revealed that heritage speakers were far more likely to extend 3PS morphology to 1PS subjects in the present perfect paradigm than in the preterite paradigm, an asymmetry that we attribute to the lower relative frequency of present perfect verb forms. In the comprehension task, participants performed similarly by extending 1PS readings to canonically 3PS inflections more often in the present perfect than in the preterite. Together, these novel results indicate that heritage speakers are more likely to extend 3PS inflections in the paradigms that they use less, a finding with key implications for our understanding of how language experience shapes the variable morphological systems that heritage speakers develop.