An Event Related Field Study of Rapid Grammatical Plasticity in Adult Second-Language Learners

Abstract

The present study used magnetoencephalography (MEG) to investigate how Spanish adult learners of Basque respond to morphosyntactic violations after a short period of training on a small fragment of Basque grammar. Participants (n = 17) were exposed to violation and control phrases in three phases (pretest, training, generalization-test). In each phase participants listened to short Basque phrases and they judged whether they were correct or incorrect. During the pre-test and generalization-test, participants did not receive any feedback. During the training blocks feedback was provided after each response. We also ran two Spanish control blocks before and after training. We analyzed the event-related magnetic- field (ERF) recorded in response to a critical word during all three phases. In the pretest, classification was below chance and we found no electrophysiological differences between violation and control stimuli. Then participants were explicitly taught a Basque grammar rule. From the first training block participants were able to correctly classify control and violation stimuli and an evoked violation response was present. Although the timing of the electrophysiological responses matched participants' L1 effect, the effect size was smaller for L2 and the topographical distribution differed from the L1. While the L1 effect was bilaterally distributed on the auditory sensors, the L2 effect was present at right frontal sensors. During training blocks two and three, the violation-control effect size increased and the topography evolved to a more L1-like pattern. Moreover, this pattern was maintained in the generalization test. We conclude that rapid changes in neuronal responses can be observed in adult learners of a simple morphosyntactic rule, and that native-like responses can be achieved at least in small fragments of second language.

Keywords: MEG; Source analysis; grammar learning; grammatical plasticity; second language acquisition.

Figure 1

Grammatical rule differences between Spanish and Basque number inflection for noun phrases. dado: die, verde/berde: green, el/los/a/ak: the, D: determiner, DS: determiner structure, Adj: adjective, AdjP: adjective phrase, NP: noun phrase, Sng: singular, Pl: plural. Arrows indicate marking relationship, thin lines dependency, double lines head dependency. See Table 1 for a translation.

Figure 2

Design of the study. Left column contains the tasks of the first session, right column tasks of the second session (Session 1 and 2 were conducted on consecutive days). Dark gray blocks are comprehension blocks (grammaticality judgement task). White blocks are production blocks (picture naming task) and light gray block is grammar rule explanation.

Figure 3

The plotted waveforms represent the averaged ERFs across all the sensors, the gray boxes the time windows where the cluster was significant and the topography plots show the raw difference between the violation and control conditions in those time windows. In order to simplify the visualization Figure 5 shows only the cluster with lowest p-value for each block. Blue waveforms correspond to the control condition, red waveforms to the violation condition. Green vertical line denote the average critical point of each block. Gray boxes indicate statistically significant time windows. The topography plots show the raw difference between the violation and control for the cluster with the most supporting evidence of that block. Blocks appear on the order they were run (A–H), with the scales given in (E).

Figure 4

Summary of the time-restricted analysis. Each horizontal box shows the significant cluster of a block (when a block had no significant cluster the one with lowest p-value is presented). First column shows the name of the block, second column the time window used for the analysis. Third column shows the source localization of the cluster. Fourth column shows whole brain raw difference between conditions (violation-control) for the given time window. And last column shows the statistical information of the given cluster: In blue the histogram of the random distribution, and the red line denotes the cluster stat value of that cluster.

Figure 5

Summary of the unrestricted analysis. Each horizontal box shows the significant cluster(s) of a block (when a block had no significant cluster the one with lowest p-value is presented). First column shows the name of the block, second column the time window where the cluster was present. Third column shows the source localization of the cluster. Fourth column shows whole brain raw difference between conditions (violation-control) for the given time window. And last column shows the statistical information of the given cluster: In blue the histogram of the random distribution, and the red line denotes the cluster stat value of that cluster.