Brain signatures of artificial language processing: Evidence challenging the critical period hypothesis

Abstract

Adult second language learning seems to be more difficult and less efficient than first language acquisition during childhood. By using event-related brain potentials, we show that adults who learned a miniature artificial language display a similar real-time pattern of brain activation when processing this language as native speakers do when processing natural languages. Participants trained in the artificial language showed two event-related brain potential components taken to reflect early automatic and late controlled syntactic processes, whereas untrained participants did not. This result challenges the common view that late second language learners process language in a principally different way from native speakers. Our findings demonstrate that a small system of grammatical rules can be syntactically instantiated by the adult speaker in a way that strongly resembles native-speaker sentence processing.

Interactions of the hippocampal system and the prefrontal cortex in learning language-like rules

“…In contrast, an early frontal effect of syntactic processing, typically observed for native speakers, was not observed for the second language learners. However, an early frontal syntax effect was reported for high proficient adult second language learners (Friederici et al, 2002). This is consistent with the present results of initial involvement of the posterior hippocampus and a shift to left inferior frontal activity associated with the proficient use of a languagelike artificial grammar.…”

“…Direct evidence for the view that learning a new artificial grammar involves language-specific processes is provided by ERP studies. Proficient usage of the artificial language used in the present experiment elicited a biphasic ERP pattern specific to natural language processing (Friederici et al, 1996(Friederici et al, , 2002. For the early, negative portion of the biphasic ERP pattern neuronal generators in the inferior fronto-lateral cortex, that is, Broca's area, have been reported (Friederici et al, 2000b).…”

“…Crucially, studies using event-related potential (ERP) measures support the view of a functional difference between nonlinguistic and linguistic grammar learning. It was shown that the pattern of brain potentials for nonlinguistic rule violations (Baldwin and Kutas, 1997) is different from those observed for the processing of violations in a linguistic artificial grammar (Friederici et al, 2002). Interestingly, the pattern of brain potentials for the latter violations is very similar to those observed for syntactic rule violations in natural language (Hahne and Friederici, 1999).…”

“…However, participants may have transferred syntactic rules from their German mother tongue to the artificial language rather than acquiring new syntactic rules. This potential transfer was controlled for by introducing two grammatical rules (determiner-noun-agreement) into BROCANTO that do not exist either in German or in any other natural language known to the participants (Friederici et al, 2002). Thus, if any observed response to syntax violations rested on a rule transfer from German to BRO-CANTO, these new rules should exhibit non-or slower learning.…”

“…The current experiment using functional magnetic resonance imaging (fMRI) set out to investigate the neural basis of artificial grammar learning by emphasizing language-like rules. Thus, in order to increase similarity between artificial grammars and natural language, the experimental design embodied an artificial language, BROCANTO (Friederici et al, 2002), that controls for a number of variables known to influence second language acquisition: (1) a large, but poorly established, vocabulary that could delay the fast availability of syntactic word category information crucial to build up syntactic structures and (2) syntactic rules which may be different between the two languages causing interference. Therefore, the present artificial grammar (cf.…”