Poster B48, Tuesday, August 20, 2019, 3:15 – 5:00 pm, Restaurant Hall
Are neural effects of composition sensitive to code-switching?
Sarah F. Phillips1, Liina Pylkkänen1,2;1New York University, 2New York University Abu Dhabi
INTRODUCTION Recent evidence has suggested that language switching incurs little cognitive effort outside artificial switching paradigms. If switching is easy, then how do our brains compute structure across language switches? We addressed this by studying two-word sentences consisting of a subject and an intransitive verb, both of which varied in the language of presentation (Korean vs. English). Our aim was to replicate a well-documented effect of composition in English, localized in the left anterior temporal lobe (LATL) at ~250ms, and then to test whether this effect is observed even when the subject and verb are presented in different languages. Observing this effect in a code-switching context would suggest that the brain has combinatory mechanisms that can operate across languages, a finding intuitively consistent with the bilingual experience. METHODS Korean-English bilinguals (n=19) read two different types of stimuli, sentences and verb-lists, during an MEG measurement. Two words that combine to form a sentence (e.g. “icicles melt”) were presented successively to elicit a composition effect, whereas two verbs that do not compose (e.g. “jump melt”) were presented as controls. Orthography also alternated for the Korean items since they can be expressed in either the Roman alphabet or Hangul. Doing so allowed us to additionally test for interactions between script, script change and composition. Source localized MEG data were analyzed with cluster-based permutation tests in four ROIs: the ATLs bilaterally, to identify composition effects, and the anterior cingulate cortex (ACC) and the dorsolateral prefrontal cortex (dlPFC), as motivated by prior research on effects of language switching in the executive control network. RESULTS A cluster-based permutation ANOVA across the full design showed a reliable main effect of composition in the left (but not right) temporal pole (BA 38) at 242-292 ms. This effect did not significantly interact with any of our other factors but pairwise comparisons revealed that it was not uniformly driven by each of the composition vs. list contrasts. Specifically, the LATL combinatory increase was only clearly observed for the stimuli in which the second element was in English. That is, English verbs showed larger LATL activity both when following an English subject or a Korean subject. When the verb was in Korean, this pattern was not observed. We speculate that this may be due to the possibility of serial verb constructions (e.g. “try speak” to mean “try to speak”) in Korean, i.e., the verb-list stimuli may have included combinatory processing in Korean but not in English. Executive control regions showed no increases for language switching, suggesting that the switches were not effortful. Instead, dlPFC showed an increase for verb-lists over sentences, likely reflecting more effortful processing for the less natural list stimuli. CONCLUSION We provide evidence that (i) combinatory operations reflected by the LATL can operate across languages and that (ii) executive control regions do not engage for language switches between a subject and its verb. For future studies on combinatory processing across code-switches, our study also highlights the challenge of designing parallel non-combinatory control conditions within different syntactic systems.
Themes: Multilingualism, Meaning: Combinatorial Semantics
Method: Electrophysiology (MEG/EEG/ECOG)