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In this article we discuss methods for investigating grammatical processing in bilinguals. We will present a methodological approach that relies on: (i) linguistic theory (in our case, morphology) for the construction of experimental materials; (ii) a design that allows for direct (within-experiment, within-participant, and within-item) comparisons of the critical conditions; and (iii) data analysis techniques that make both linear and non-linear gradient effects visible. We review recent studies of masked morphological priming in bilinguals in which the application of these methodological principles revealed highly selective interactions of age of acquisition (and the native/non-native contrast) with the linguistic distinction between inflection and derivation. We believe that such considerations are not only relevant for grammatical processing experiments, but also for studying bilingualism, and its potential cognitive advantages, more generally.
Background: Word retrieval in aphasia involves different levels of processinglemma retrieval, grammatical encoding, lexeme retrieval, and phonological encodingbefore articulation can be programmed and executed. Several grammatical, semantic, lexical, and phonological characteristics, such as word class, age of acquisition, imageability, and word frequency influence the degree of success in word retrieval. It is, however, not yet clear how these factors interact. The current study focuses on the retrieval of nouns and verbs in isolation and in sentence context and evaluates the impact of the mentioned factors on the performance of a group of 54 aphasic speakers.Aims: The main aim is to measure the effect of word frequency on the retrieval of nouns and verb by disentangling the influence of word class, age of acquisition, imageability, and lemma and lexeme frequencies on word retrieval in aphasia.Methods & Procedures: Four tests for retrieval of nouns, verbs in isolation, and infinitives and finite verbs were administered to 54 aphasic speakers. The influence of lemma and lexeme frequency, Age of Acquisition on the word retrieval abilities was analysed.Outcomes and Results: Word class, age of acquisition, and imageability play a significant role in the retrieval of nouns and verbs: nouns are easier than verbs; the earlier a word has been learned and the more concrete it is, the easier it is to retrieve. When performance is controlled for these factors, lemma frequency turns out to play a minor role: only in object naming does it affect word retrieval: the higher the lemma frequency of a noun, the easier it is to access. Such an effect does not exist for verbs, neither on an action-naming test, nor when verbs have to be retrieved in sentence context. Lexeme frequency was not found to be a better predictor than lemma frequency in predicting word retrieval in aphasia.Conclusions: Word retrieval in aphasia is influenced by grammatical, semantic, and lexical factors. Word frequency only plays a minor role: it affects the retrieval of nouns, but not of verbs.
Early acquisition of a second language influences the development of language abilities and cognitive functions. In the present study, we used functional Magnetic Resonance Imaging (fMRI) to investigate the impact of early bilingualism on the organization of the cortical language network during sentence production. Two groups of adult multilinguals, proficient in three languages, were tested on a narrative task; early multilinguals acquired the second language before the age of three years, late multilinguals after the age of nine. All participants learned a third language after nine years of age. Comparison of the two groups revealed substantial differences in language-related brain activity for early as well as late acquired languages. Most importantly, early multilinguals preferentially activated a fronto-striatal network in the left hemisphere, whereas the left posterior superior temporal gyrus (pSTG) was activated to a lesser degree than in late multilinguals. The same brain regions were highlighted in previous studies when a non-target language had to be controlled. Hence the engagement of language control in adult early multilinguals appears to be influenced by the specific learning and acquisition conditions during early childhood. Remarkably, our results reveal that the functional control of early and subsequently later acquired languages is similarly affected, suggesting that language experience has a pervasive influence into adulthood. As such, our findings extend the current understanding of control functions in multilinguals.