Age is considered an important factor for the acquisition of new skills in the domain of language and in other perceptual and cognitive competences. Clear evidence of age of acquisition (AoA) effects has been found in the development of sensory systems, supporting the idea that speciﬁc brain functions can develop only during an early critical period, characterized by brain plasticity. The crucial role of infancy for the acquisition of basic language competences is supported by clear findings involving first language (L1) but its extension to second (L2) and further languages is controversial. Can adult people learn new languages and reach native-like skills? What factors or condition favor the acquisition of high proficiency in the new language? Experimental studies suggest that implicit learning and continued language use are major factors inﬂuencing bilingual proﬁciency.
According to the Declarative/Procedural Model (Ullman, 2001), language processing mainly includes: a mental lexicon, depending on declarative memory, a set of grammatical rules, and phonology, which both mainly depend on procedural memory. Accordingly, L1 acquisition extensively relies on implicit learning and procedural memory while L2 acquisition involves explicit learning and declarative memory. The convergence hypothesis (Green, 2003) suggests that these differences decrease when proficiency increases. However, beyond lexicon, grammar and phonology, verbal communication also involves pragmatic competences, enabling the use of sentences appropriate to the context, including ﬁgurative, metaphoric and idiomatic expressions. Another pragmatic competence concerns the communication in bilingual mode and entails the ability to switch between languages without code-mixing and interferences.
We present a study aimed at verifying the effect of AoA and intensity of language use on proﬁciency in a bilingual task and its relationship with cognitive skills. The study involved a group of Italian–Spanish bilinguals who performed a battery of cognitive tests and a bilingual test mainly involving pragmatic and lexical competences but not phonetics: it required the fast recognition of whole sentences having the same functional meaning in the two languages, so stimulating automatic language processing and switching. Statistical analysis showed signiﬁcant effects of language use and cognitive skills, mainly switching and executive control, and a non-signiﬁcant effect of AoA. These results indicate that intensive bilingual practice is a major factor inﬂuencing pragmatic bilingual proﬁciency, even irrespective of AoA, also suggesting that proﬁciency may be weakened when bilingual experience becomes occasional or ceases. The study also confirms the association between bilingual proficiency and cognitive skills which might reflect a positive reciprocal influence.