Date of Degree

2-2017

Document Type

Dissertation

Degree Name

Ph.D.

Program

Speech-Language-Hearing Sciences

Advisor(s)

Loraine K. Obler

Klara Marton

Committee Members

Mira Goral

Subject Categories

Psycholinguistics and Neurolinguistics

Keywords

Bilingual language control, language switching, inhibition, asymmetry in switch costs, immersion context

Abstract

Bilingual speakers are assumed to activate two languages during language comprehension and production even when the input or output is in only one language. The parallel activation of both languages may result in competition between languages (e.g., Costa et al., 2006, Kroll, Bobb, & Wodniecka, 2006, La Heij, 2005). Earlier studies examined how the two languages are processed and controlled by mitigating interference during language selection (e.g., Abutalebi & Green, 2008; Marian & Spivey, 2003; Poulisse, 1999).

One way to study language control processes is to examine language-switching behaviors, a unique marker for these control processes (e.g., Bobb & Wodniecka, 2013). Although some earlier studies reported asymmetrical switch costs (i.e., larger switch cost from L2 to L1 than from L1 to L2), which were thought to reflect the role of inhibitory control in bilingual speech, more recent findings have been mixed, indicating that the nature of language control remains controversial (e.g., Calabria et al., 2012; Costa, Santesteban & Ivanova, 2006). Moreover, recent findings concerning bilingual language control imply that both language suppression and activation contribute to interference control during switching, leaving other potential control processes largely under-investigated (compared to the notion of inhibitory control; e.g., Christoffels et al., 2007).

The current study aimed to understand how the control mechanism operates in specific switching contexts by (a) manipulating the degree of switch frequency, which stimulates a more or less competitive language switching context, and (b) contrasting language predominance, which signals a more L1 dominant versus L2 dominant switching context. Forty-four Korean-English bilinguals living in the United States performed a picture naming task in which the retrieval of words from each language varied according to the experimental manipulations.

The data were analyzed to explore possible effects of switch-frequency and language predominance. The bilingual speakers exhibited an overall naming advantage for English in both baseline and experimental conditions, independent of individual language proficiency. Moreover, a clear effect of switch frequency was seen (less frequent switches resulted in a greater local switch cost) while there was no effect of language predominance (similar patterns of switch costs were reported in both conditions). Particular task demands associated with levels of competition via switch frequency modulated levels of interference, resulting in different degrees of local vs. global switch costs within bilingual individuals. In conclusion, the current findings suggest that the language environment (immersion context), as well as the experimental task conditions varying by switch frequency have an effect on the bilingual language control mechanism.

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