  Citation: Camacho, José. 2022. Paradigmatic Uniformity: Evidence from Heritage Speakers of Spanish. Languages 7: 14. https://doi.org/ 10.3390/languages7010014 Academic Editors: Esther Rinke and Gabriel Martínez Vera Received: 27 August 2021 Accepted: 27 December 2021 Published: 13 January 2022 Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affil- iations. Copyright: © 2022 by the author. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). languages Article Paradigmatic Uniformity: Evidence from Heritage Speakers of Spanish José Camacho Hispanic and Italian Studies, University of Illinois Chicago, Chicago, IL 60607, USA; jcamach@uic.edu Abstract: Subject-verb agreement mismatches have been reported in the L2 and heritage literature, usually involving infinitives, analyzed as default morphological forms for fully specified T-heads. This article explores the mechanisms behind these mismatches, testing two hypotheses: the default form and the surface-similarity hypotheses. It compares non-finite and finite S-V mismatches with subjects with different persons, testing whether similarity with other paradigmatic forms makes them more acceptable, controlling for the role of verb frequency. Participants were asked to rate sentences on a Likert scale that included (a) infinitive forms with first, second and third person subjects, and (b) third person verbal forms with first, second and third person subjects. Two stem-stressed verbs (e.g., TRA.j-o ‘brought.3P. PAST’) and two affix-stressed verbs (e.g., me.ti-O ‘introduced.3P. PAST’), varying in frequency were tested. Inflectional affixes of stem-stressed verbs are similar to other forms of the paradigm both phonologically and in being unstressed (TRA.j-o ‘brought.3P. PAST’ vs. TRAI.g-o ‘bring.1 P. PRES’), whereas affixes of affix-stressed verbs have dissimilar stress patterns (me.ti-O ´introduced.3P. PAST’ vs. ME.t-o ‘introduce.1P. PRES’). Results show significantly higher acceptability for finite vs. non-finite non-matching, and for 1st vs. 2nd person subjects. Stem-stressed verbs showed higher acceptability ratings than affix-stressed ones, suggesting a role for surface-form correspondence, partially confirming previous findings. Keywords: agreement mismatches; morphology; output-to-output correspondence; surface-form networks; frequency effects; heritage speakers 1. Introduction Spanish has a generalized agreement between the subject and the verb, realized as systematic variation in the inflectional morphology of the verb depending on the features of the subject. For example, in (1)a, -o encodes 1st person singular on the verb to match the person features of the subject, whereas in (1)b, the affix -e indicates 3rd person singular to match a 3rd person subject. The property of agreement is thus indirectly encoded in the inflectional morphology of the verb. In certain cases, verbal morphology is not completely transparent in the sense that the same morpheme can encode different person/tense combinations, as seen in (2), where the affix for a 1st person, present tense is the same as the affix for a 3rd person preterit. (1) a. Yo com-o. I eat-1SG ‘I eat.’ b. Ella com-e. she eat-3SG ‘She eats.’ (2) a. Yo traig-o. I bring-1SG. PRES ‘I bring.‘ b. Ella traj-o she brought–3SG. PAST Languages 2022, 7, 14. https://doi.org/10.3390/languages7010014 https://www.mdpi.com/journal/languages