Bilingualism in Jamaica is of considerable consequence, as most individuals are early bilinguals, speaking both a variety of Jamaican Creole (JC) from birth and having standardized English (sE) as the language of instruction in education. Immigrants from Jamaica to the United States are an ideal population to examine how cross-linguistic influence (CLI) impacts morphosyntax as JC and sE differ in morphosyntactic constructions, including verb tense-marking, subject-verb agreement, and copula use. While much of the work in the field of CLI has examined spoken language pairs with varying degrees of similarity (or difference) between the languages, examining CLI in a language paired with a creole lexified from that language has yet to be investigated. This study investigated whether CLI of morphosyntax, including verb tense-marking, subject-verb agreement, and copula inclusion, is bidirectional; that is, whether CLI can be observed between the L1 (Jamaican Creole) to the L2 (standardized English, sE) in both directions. We examined sentences and narratives for two groups of bilingual speakers--an Immigrant group residing in the U.S. and a Non-immigrant group residing in Jamaica--to analyze morphosyntactic production. We also investigated which internal and external factors contribute to bidirectional CLI. Evaluating language samples collected from bilingual speakers on controlled and less controlled tasks, we reasoned, provides a unique opportunity to observe how these two languages might influence each other in the same speaker. Our findings show bidirectional CLI in both groups, with the Immigrant group exhibiting more cross-linguistic influence from the L2 to the L1. By contrast, the Non-immigrant group exhibited greater L1 to L2 CLI than the Immigrant group, possibly as a result of greater use of the L1. Sociolinguistic factors were analyzed and indicated that variables linked to increased language use in either the L1 or L2 resulted in more CLI from that language. This study provides valuable information about the variation in both Jamaican Creole and Jamaican English. This information is crucial to understanding how healthy adult bilingual speakers of Jamaican Creole and Jamaican English produce morphosyntax, which will benefit our understanding of what occurs in adults with acquired language disorders. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com/en-US/products/dissertations/individuals.shtml.]