Electrophysiological Correlates of Second-Language Syntactic Processes Are Related to Native and Second Language Distance Regardless of Age of Acquisition

Abstract

In the present study, we investigate how early and late L2 learners process L2 grammatical traits that are either present or absent in their native language (L1). Thirteen early (AoA = 4 years old) and 13 late (AoA = 18 years old) Spanish learners of Basque performed a grammatical judgment task on auditory Basque sentences while their event-related brain potentials (ERPs) were recorded. The sentences contained violations of a syntactic property specific to participants' L2, i.e., ergative case, or violations of a syntactic property present in both of the participants' languages, i.e., verb agreement. Two forms of verb agreement were tested: subject agreement, found in participants' L1 and L2, and object agreement, present only in participants' L2. Behaviorally, early bilinguals were more accurate in the judgment task than late L2 learners. Early bilinguals showed native-like ERPs for verb agreement, which differed from the late learners' ERP pattern. Nonetheless, approximation to native-likeness was greater for the subject-verb agreement processing, the type of verb-agreement present in participants' L1, compared to object-verb agreement, the type of verb-agreement present only in participants' L2. For the ergative argument alignment, unique to L2, the two non-native groups showed similar ERP patterns which did not correspond to the natives' ERP pattern. We conclude that non-native syntactic processing approximates native processing for early L2 acquisition and high proficiency levels when the syntactic property is common to the L1 and L2. However, syntactic traits that are not present in the L1 do not rely on native-like processing, despite early AoA and high proficiency.

Keywords: P600; age of acquisition; bilingualism; event-related potentials; language distance; morphosyntax.

Figure 1

Participants' global hit rate for early bilinguals and late L2 learners.

Figure 2

Results of the t-tests on 50-ms consecutive intervals comparing grammatical and ungrammatical sentences at each electrode and for each condition for early and late bilinguals. The beginning of the epochs are time-locked to the onset of the critical words (i.e., the auxiliary verb for the subject- and object-agreement conditions and the ergative case marker of the second nominal phrase for the ergative case condition). Significant differences between the grammatical and ungrammatical sentences are indicated by the color bars: Red bars correspond to positive effects and blue bars correspond to negative effects. Discontinuous vertical lines mark the onset and offsets of the significant periods. Gray areas indicate the significant time windows.

Figure 3

Grand average waveforms of the early and late groups at four representative electrodes distributed across each scalp area analyzed (frontal right: F4, frontal left: F3, posterior right: P4, posterior left: P3). Grand averages are time-locked to the onset of the critical words, i.e., the auxiliary verb for subject- and object-agreement conditions and the morpheme marking the ergative case for the ergative case condition (critical words are depicted in bold in the figure legend). Bars depict the time windows where grammatical and ungrammatical sentences elicited significantly different ERPs. Gray bars depict similar effects between the two groups, and purple bars depict effects which are unique to the given non-native group.