Theses and Dissertations from UMD
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Item SELECTIVITY IN LEXICAL ACCESS AMONG BILINGUALS OF ORTHOGRAPHICALLY DISTINCT SCRIPTS AND THE ROLE OF EXECUTIVE FUNCTIONS(2020) Al Thowaini, Buthainah M; Jiang, Nan; Second Language Acquisition and Application; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)A fundamental inquiry within bilingual processing research addresses the underlying mechanisms of lexical access. Research involving bilinguals of orthographically similar scripts has revealed that cross-language activation is non-selective, which supposedly causes the bilingual brain to regularly manage the activation of two languages. Such continuous management of two languages has led some researchers to argue that the bilingual experience contributes to enhanced executive control. The research on selectivity in lexical access, nevertheless, has overwhelmingly involved bilingual speakers of orthographically similar scripts, with a scarcity of studies involving bilingual speakers of orthographically distinct scripts. Additionally, while active management of both languages is expected for bilinguals, little is known about whether language selectivity is related to individual variation in executive control. Instead, research investigating executive functions (EFs) in relation to bilingual processes has primarily been conducted within the context of switch costs, which has been associated with methodological issues. In light of the issues outlined above, the current study investigated selectivity in lexical access among bilinguals of orthographically distinct scripts and the relationship between the degree of selectivity and EFs (i.e., top-down goal maintenance, interference resolution, and working memory capacity). In addition to adopting an individual differences approach to lexical access, the study manipulated the degree of language task demands (comprehension and production). The study employed alternative non-switch tasks to investigate the relationships between EFs and cross-language activation. One hundred and thirty-eight Arabic-English bilinguals, 25 English native speakers, and 24 Arabic native speakers participated in a phoneme monitoring task and a masked primed lexical decision task involving monolingual materials. Bilingual participants also completed non-verbal visuo-spatial and visual single n-back tasks, as well as an AX-CPT task. The analyses revealed non-selective lexical access in language production but were inconclusive for language comprehension, where participants varied in the degree of selectivity. In addition, the results, although preliminary, demonstrated that top-down goal maintenance partially accounted for some of the variances in the degree of selectivity in language comprehension and production. The results suggest that selectivity is influenced by task-dependent variables as well as individual differences in executive functions.Item Form, meaning and context in lexical access: MEG and behavioral evidence(2009) Almeida, Diogo; Poeppel, David; Linguistics; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)One of the main challenges in the study of cognition is how to connect brain activity to cognitive processes. In the domain of language, this requires coordination between two different lines of research: theoretical models of linguistic knowledge and language processing on the one side and brain sciences on the other. The work reported in this dissertation attempts to link these two lines of research by focusing on one particular aspect of linguistic processing, namely lexical access. The rationale for this focus is that access to the lexicon is a mandatory step in any theory of linguistic computation, and therefore findings about lexical access procedures have consequences for language processing models in general. Moreover, in the domain of brain electrophysiology, past research on event-related brain potentials (ERPs) - electrophysiological responses taken to reflect processing of certain specific kinds of stimuli or specific cognitive processes - has uncovered different ERPs that have been connected to linguistic stimuli and processes. One particular ERP, peaking at around 400 ms post-stimulus onset (N400) has been linked to lexico-semantic processing, but its precise functional interpretation remains controversial: The N400 has been proposed to reflect lexical access procedures as well as higher order semantic/pragmatic processing. In a series of three MEG experiments, we show that access to the lexicon from print occurs much earlier than previously thought, at around 200 ms, but more research is needed before the same conclusion can be reached about lexical access based on auditory or sign language input. The cognitive activity indexed by the N400 and its MEG analogue is argued to constitute predictive processing that integrates information from linguistic and non-linguistic sources at a later, post-lexical stage.