The acquisition of a heritage language, normally the weaker language of early bilinguals, has been oftentimes defined as incomplete, especially for morphosyntax. As a result, these early bilinguals resemble late bilinguals more than native language speakers, calling into question the role of age of exposure. The effects of syntactic complexity on knowledge of morphosyntactic structures, however, have not been sufficiently considered hitherto. This study investigates age of exposure and syntactic complexity by comparing heritage, second language, and native language speakers on knowledge of Italian accusative clitics in three structures. An oral structural priming task and a speeded grammaticality judgment task find a discrepancy in the level of ultimate attainment heritage speakers reach for syntax and morphology. While their abstract representation of clitic structures approximates that of native language speakers more closely, their morphological knowledge of clitics aligns with second language speakers, suggesting early exposure has tangible effects only on syntactic knowledge. In turn, syntactic complexity affects the representation of clitic structures in a predictable manner, but is inconsequential to explicit knowledge of morphological forms in monolingual and bilingual speakers. Lack of age of exposure effects in the morphological domain are attributed to interface vulnerability.

中文翻译：

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传统语言使用者的终极成就：意大利宾格的句法和形态知识

传统语言的习得，通常是早期双语者较弱的语言，经常被定义为不完整的，特别是对于形态句法。结果，这些早期的双语者比母语者更像晚期的双语者，这对暴露年龄的作用提出了质疑。然而，句法复杂性对形态句法结构知识的影响迄今尚未得到充分考虑。本研究通过比较遗产、第二语言和母语使用者对三种结构中意大利宾格附体的知识，调查暴露年龄和句法复杂性。一项口头结构启动任务和一项加速语法判断任务发现，在最终成就遗产说话者达到句法和形态学的水平上存在差异。虽然他们对附着体结构的抽象表示更接近于母语使用者，但他们对附着体的形态学知识与第二语言使用者一致，这表明早期接触仅对句法知识有实际影响。反过来，句法复杂性以可预测的方式影响附着体结构的表示，但与单语和双语者对形态形式的明确了解无关紧要。在形态学领域缺乏暴露效应的年龄归因于界面脆弱性。句法复杂性以可预测的方式影响附着体结构的表示，但与单语和双语者对形态形式的明确知识无关。在形态学领域缺乏暴露效应的年龄归因于界面脆弱性。句法复杂性以可预测的方式影响附着体结构的表示，但与单语和双语者对形态形式的明确知识无关。在形态学领域缺乏暴露效应的年龄归因于界面脆弱性。