Early neurophysiological indices of second language morphosyntax learning

Jeff Hanna,Yury Shtyrov,John Williams,Friedemann Pulvermüller

doi:10.1016/j.neuropsychologia.2016.01.001

Abstract

Humans show variable degrees of success in acquiring a second language (L2). In many cases, morphological and syntactic knowledge remain deficient, although some learners succeed in reaching nativelike levels, even if they begin acquiring their L2 relatively late. In this study, we use psycholinguistic, online language proficiency tests and a neurophysiological index of syntactic processing, the syntactic mismatch negativity (sMMN) to local agreement violations, to compare behavioural and neurophysiological markers of grammar processing between native speakers (NS) of English and non-native speakers (NNS). Variable grammar proficiency was measured by psycholinguistic tests. When NS heard ungrammatical word sequences lacking agreement between subject and verb (e.g. *we kicks), the MMN was enhanced compared with syntactically legal sentences (e.g. he kicks). More proficient NNS also showed this difference, but less proficient NNS did not. The main cortical sources of the MMN responses were localised in bilateral superior temporal areas, where, crucially, source strength of grammar-related neuronal activity correlated significantly with grammatical proficiency of individual L2 speakers as revealed by the psycholinguistic tests. As our results show similar, early MMN indices to morpho-syntactic agreement violations among both native speakers and non-native speakers with high grammar proficiency, they appear consistent with the use of similar brain mechanisms for at least certain aspects of L1 and L2 grammars.

Highlights

English (NS) and non-native speakers of English (NNS) of varying proficiency
This research has produced the following key findings: (1) the syntactic Mismatch Negativity, an early brain index of grammar processing not requiring focused attention, has been observed in response to subject–verb agreement violations perceived by some speakers of a late acquired second language (English). sMMNm responses similar to those in native speakers (NS) were present in non-native speakers with high grammar proficiency (HP), but not in low proficient non-native speakers (LP). (2) sMMNm strength in non-native speakers significantly correlated with the level of syntactic-grammatical knowledge and performance in their L2 as measured by online psycholinguistic syntax experiments (PC1). (3) The lack of verb inflection and subject–verb agreement in the NNS groups' L1 (Chinese) did not impede them from developing a fast, automatic capability for comprehending it
We found that the cortical sources of the sMMNm in bilateral superior-temporal cortex of non-native speakers of English correlated with their syntactic proficiency, as revealed by a newly explored assembly of online psycholinguistic tests

Summary

Introduction

English (NS) and non-native speakers of English (NNS) of varying proficiency. Our results show that, among NNS, level of grammatical proficiency in processing subject–verb agreement-as assessed by experimental psycholinguistic methods-is reflected in this brain response.Previous neurophysiological work on L2 syntax acquisition has mostly used one or more of three event-related potentials, each of which is thought to index aspects of syntactic processing: the early left anterior negativity (ELAN) appearing at around 150 ms after critical stimulus onset, the left anterior negativity (LAN) at around 300–500 ms, and the slow positive shift, or P600, at around 300– 900 ms (Kutas et al, 2006). A handful of studies found that ERP responses were modulated by both AoA and proficiency (Dowens et al, 2009; Hahne, 2001; Hahne and Friederici, 2001) The results of this majority of studies converges with suggestions that grammar proficiency might not primarily depend on the age when language is learnt, but, instead, on other factors, including motivation and sociocultural embedding (Schumann et al, 2004), level of education (Dabrowska and Street, 2006), amount of learning (DeKeyser, 2007) and so on (Abrahamsson and Hyltenstam (2009), Birdsong (2006) and DeKeyser (2013) for discussion)

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