Are All Code-Switches Processed Alike? Examining Semantic v. Language Unexpectancy

Abstract

Prior studies using the event-related potential (ERP) technique show that integrating sentential code-switches during online processing leads to a broadly distributed late positivity component (LPC), while processing semantically unexpected continuations instead leads to the emergence of an N400 effect. While the N400 is generally assumed to index lexico-semantic processing, the LPC has two different interpretations. One account suggests that it reflects the processing of an improbable or unexpected event, while an alternative account proposes sentence-level reanalysis. To investigate the relative costs of semantic to language-based unexpectancies (i.e., code-switches), the current study tests 24 Spanish-English bilinguals in an ERP reading study. Semantically constrained Spanish frames either varied in their semantic expectancy (high vs. low expectancy) and/or their language continuation (same-language vs. code-switch) while participants' electrophysiological responses were recorded. The Spanish-to-English switch direction provides a more naturalistic test for integration costs to code-switching as it better approximates the code-switching practices of the target population. Analyses across three time windows show a main effect for semantic expectancy in the N400 time window and a main effect for code-switching in the LPC time window. Additional analyses based on the self-reported code-switching experience of the participants suggest an early positivity linked to less experience with code-switching. The results highlight that not all code-switches lead to similar integration costs and that prior experience with code-switching is an important additional factor that modulates online processing.

Keywords: N400; bilingual (Spanish/English); code-switching; event-related potentials; late positive complex; semantic processing.

Figure 1

(A) Event-related potentials (ERPs) locked to the noun in electrodes representative of each area of interest in the midline: Fz for the frontal, Cz for the central, and Pz for the posterior regions. Targets that are not switched (nS) are depicted with a dashed line when they are semantically low expected (LE) and with a solid line when they are semantically highly expected (HE); for nouns that are code-switched (S), LE nouns are depicted with a bold dashed line and HE nouns with a bold solid line. Boxes indicate time windows included in the analyses. (B) Electrodes grouped in two topographical factor regions of Laterality (left, midline, and right electrodes) and Anterior/Posterior (anterior, central, and posterior electrodes) included in the analyses.

Figure 2

The Expectancy effect in Fz, Cz, and Pz electrodes. Boxes indicate time windows included in the analysis and dark outlines the regions where the effect is statistically significant.

Figure 3

Switched vs. non-switched conditions in Fz, Cz, and Pz electrodes. Boxes indicate time windows included in the analysis and dark outlines the regions where the effect is statistically significant.

Figure 4

The baseline (non-switched, highly expected continuation) vs. the double unexpectancy (code-switched and semantically unexpected continuation) in Fz, Cz, and Pz electrodes. Boxes indicate time windows included in the analysis and dark outlines the regions where the effect is statistically significant.