1. Introduction It is widely accepted that bilinguals experience a code-switching cost when the language of the stimuli changes unexpectedly. Where in the language-processing stream do these costs occur? Grainger & Beauvillain (1987) found that code- switching costs could be eliminated in the presence of language-specific orthographic cues, suggesting that these costs occur during lexical access. However, Thomas & Allport (2000) found that, by adding a control condition, code-switching costs were not eliminated by the presence of language-specific orthography, placing these costs outside the lexicon (that is, in control processes not specific to lexical access). How do these costs differ as fluency increases? Figure 2 – Electrode Montage Investigating the Automaticity of Code-Switching in Proficient Bilinguals Using Masked Priming: An Event-Related Potentials Study Krysta Chauncey 1, Katherine J. Midgley 1, Jonathan Grainger 1,2, Phillip J. Holcomb 1 1 Tufts University, Medford, MA; 2 LPC-CNRS, Université de Provence narine - LOANBetweenEnglish dust - LOANWithinEnglish loan - LOANRepetitionEnglish folk - SOLEILBetweenFrench cheveu - SOLEILWithinFrench soleil - SOLEILRepetitionFrench StimuliTypeLanguage Figure 3 – Trial Types Figure 6 – F1 population, L2 repetition effect, CP1 electrode Figure 7 – F2 population, L2 repetition effect, CP1 electrode English (L2) repetition trials English (L2) within trials Figure 8 – F1 population, L1-L2 code-switching effect, CP1 electrode English (L2) within trials French prime, English target trials Figure 9 – F2 population, L1-L2 code-switching effect, CP1 electrode English (L2) within trials French prime, English target trials English (L2) within trials English (L2) repetition trials

2. Methods Subjects right-handed native speakers of French normal or corrected-to-normal vision F1 population: 20 subs (11 females, avg age = 20.7) academic instruction only in English F2 population: 13 subs (5 males, avg age = 21.7) avg. 3 years immersion in English Stimuli common words in English and French blocked by target language, order counterbalanced words rotation through positions in 5 lists 50 trials each of three types in each language Repetition trials Within-language non-repetition trials Between-language code-switching trials Task semantic categorization judgment to animals This research was supported by NIH Grants HD25889 and HD43251 References Alvarez, R., Holcomb, P., & Grainger, J. (2003). Accessing word meaning in two languages: An event-related brain potential study of beginning bilinguals. Brain and Language, 87(2), 290-304. Grainger, J. & Beauvillain, C. (1987). Language blocking and lexical access in bilinguals. Quarterly Journal of Experimental Psychology, 39A, 295-319. Thomas, M. & Allport, A. (2000). Language switching costs in bilingual visual word recognition. Journal of Memory & Language, 43: 44-66. Conclusions Code-switching effect for L2-L1 found in N400 suggests limited automatic processing of L2 No repetition effect of L2 (English) found in F1, but found in F2, suggests greater automatic processing with increased fluency Additional L1-L2 code-switching cost in N400 window for more competent population suggests greater semantic processing for L2 Results In L1-based (French) trials, consistent results in N400 window between populations (Repetition = Within < Between) In L2-based (English) trials, Pop F1: No repetition effect in N400 window, but code-switching effect Pop F2: Repetition effect in N400 window, as well as code-switching For pop F1, greater code-switching cost in the N400 window for L2-L1 switches, but for L1-L2 cost greater in the N250 window for L1-L2 switches For pop F2, L2-L1 switches also produced costs in the N400 window, but L1-L2 costs occur in both N250 and N400 window Fig. 1: Trial schema Figure 4 – F2 population, L2-based Trial Types Figure 5 – F2 population, L1-based Trial Types Cz CP1 Cz CP2 Pz Oz Pz CP1CP2 English (L2) repetition trials French (L1) repetition trials English (L2) within trials French prime, English target trials French (L1) within trials English prime, French target trials