Inhibitory control in bilingualism

Resumen

The studies included in this dissertation aimed mainly to investigate the involvement of inhibitory mechanisms on language selection in Spanish-English bilinguals (L1: Spanish; L2: English) by using a semantic relatedness judgment task in which word pairs of English words were presented including interlexical homographs as critical stimuli (e.g., ¿pie¿ means foot in Spanish and cake in English). The paradigm we used is an adaptation of the negative priming task developed in blocks of two trials, which allowed us to take two different indexes or measures. On one hand, we considered the interference effect in response to word pairs including homographs (i.e., first trial of the block) as an index of the non-selective activation of both meanings of a homograph. On the other hand, we considered the delay to response to trials that require the reactivation of the irrelevant meaning of the homograph (i.e., second trial of the block), presented in a previous trial, as an index of the homograph non-target meaning inhibition. Using this paradigm, we carried out a series of studies to address more specific goals: (1) we aimed to gather evidence of the presence of inhibitory processes while Spanish-English bilinguals selected the English meaning of interlexical homographs; (2) we to explore the cortical activity associated to the cross-language effects observed; (3) we explored whether the inhibitory processes involved in language selection extend in time; (4) we investigated whether immersion in a second language environment and expertise in professional translation modulate between-language activation and the control processes involved in language selection. The findings in this dissertation showed that bilinguals activated the two homograph meanings showing the interference effect. Importantly, after activating the two meanings of a homograph, bilinguals slowed their responses when its Spanish meaning became relevant in the second trial, indicating that this irrelevant meaning was inhibited. This inhibitory effect was observed (1) after responding to homographs in the previous trial, (2) when the non-target meaning of the homograph previously presented became relevant in the following trial, and (3) when the interlexical homographs were presented both embedded in word pairs and in isolation. We also observed an ERP modulation associated to the processing of homographs with a latency and scalp distribution corresponding to the typical N400 time window. The pattern of results showed that the inhibitory effects were very short lived since they were observed in a time interval between 500 ms and 750 ms. After a time interval of 750 ms, bilinguals seem to have recovered from inhibition. Finally, we observed a modulator effect of the language immersion context and the expertise in translation of the bilinguals on language activation and language selection processes. While the L2 immersed bilinguals showed no interference effect and no between-language competition, the translators showed the interference responding to homographs but no inhibitory effect. In sum, the empirical findings reported in this work provide further evidence for the theoretical perspective that the lexical access in bilinguals is fundamentally language non-selective (Dijkstra, 2005) and agree with the inhibitory hypothesis of meaning selection in bilingual language comprehension (Green, 1998). The ERP modulation associated with the processing of interlexical homographs further supports at the electrophysiological level the behavioural findings. The findings regarding the time course of language control processes suggest that inhibition seems to be a process involved in the resolution of between-language competition, and this inhibition has a transient effect. Finally, we observed that the immersion in a second language context and the expertise in translation are important factors that might impact on bilingual language processing.