L ITERATURE R EVIEW
2.4 Research on Processing
2.4.1 Lexical Access: Selective or Non-selective?
2.4.1.2 The Influence of Age of Acquisition and Proficiency
To put in a nutshell, the three theoretical explanations on cognate facilitation effect have different ways of interpretation and predictions. The morphological account attributes the facilitation to the underlying representational difference between cognates and non-cognates. The form overlap account from connectionist models argues that cognate facilitation arises because besides shared semantics, cognates have additional shared form overlaps. If cognate facilitation arises out of form overlaps, cognate facilitation should disappear when the influence of form overlaps is taken out. Further, if form overlap does not affect processing, cognate facilitation will not exist either. Finally, the link account attributes the facilitation effect to stronger link at the lexical level and thus predicts cognate facilitation regardless of task. To sum up, extensive research in the field of bilingual lexical processing has demonstrated that the two languages of a bilingual can interact at various levels.
Moreover, the way bilinguals can vary as a result of their age of acquisition and proficiency can also influence the co-activation of languages. In the following section, we address this issue of whether differences in second language age of acquisition and proficiency can affect the representation and processing of languages in bilinguals.
(1967) and adopted to explain age-dependent differences in L2 learning by Johnson and Newport (1989) states that after a certain age, the ability to acquire an L2 is greatly diminished or lost. Birdsong (1999) succinctly defined the term as:
There is a limited developmental period during which it is possible to acquire a language, be it L1 or L2, to normal native like levels. Once this window of opportunity is passed, however, the ability to learn languages declines. (p. 1)
The issue of how the cutoff for early and late AoA is determined has also been a much debatable issue. Past studies have used a variety of ages to categorize late AoA groups, ranging from 6 to 16 years of age (Kim, Relkin, Lee, & Hirch, 1997).
Indeed, some researchers suggest that results in support of a critical period are simply confounded with other predictive factors, such as amount of L2 education, chronological age, and L2 language exposure (Flege, Yeni-Komshian, & Liu, 1999).
This implies that dividing subjects into two groups of early and late acquisition may not be appropriate, and treating AoA as a continuous variable may allow for a more complete and accurate description of the effects of AoA on L2 processing. As put forward by De Groot (2011):
To anticipate, the results of these studies suggest that the human ability to learn language remains intact throughout life as long as it is fed by early linguistic experience. If it is not nourished in this way, the proficient use of languages learned later in life seems beyond reach. (p. 59)
Over the years, numerous studies which have made use of different tasks and paradigms have demonstrated differences in processing as a function of second language age of acquisition. For example, Kim et al., (1997), Weber-Fox & Neville (1999) and Wuillemin & Richardson (1994) have shown contrasts between early and late bilinguals. Similarly, in 2002, Izura and Ellis found that second language words which were learned at an early stage had a processing advantage over words which were learned at a later stage. In other words, the majority of the studies in the past have investigated bilinguals differing in their second language age of acquisition.
This raises another important question as to what extent the representation and processing of the bilingual’s two languages modulated by differences in second language proficiency?
Studies investigating the role of proficiency in bilingual lexical representation and processing have examined bilinguals with different levels of proficiency in their second language. Several studies investigating the degree of co-activation and interaction between the two languages of a bilingual have observed that variation in second language proficiency differentially affects cross-language interactions at various levels. For example, studies employing cross-language semantic priming and translation priming paradigms have observed that differences in proficiency affect semantic and translation priming effects (Frenck and Pynte, 1987). The findings of these studies are in line with the assumptions of the Revised Hierarchical model. In contrast, studies employing cross-language masked phonological priming paradigm have observed that differences in second language proficiency does not affect phonological priming effect (Duyck, Diependaele, Drieghe,and Brysbaert, 2004).
Moreover, the fact that age of acquisition and proficiency are highly intertwined complicates the situation even more. For example, the influence of both factors has been observed in Silverberg and Samuel’s (2004) study. In their study, they tested Spanish−English bilinguals differing in their second language age of acquisition and proficiency in a semantic priming task. The results showed that significant semantic priming effects were evident only in case of early high proficient bilinguals, whereas, late proficient bilinguals, regardless of their second language proficiency failed to produce any priming effects.
The issue of how the representation and processing of bilingual’s two languages differ as a result of their second language age of acquisition and proficiency has been described by several theories and models. However, most of these theories and models deal with high proficient bilinguals. The Revised Hierarchical Model is among the few developmental models that provided an interesting perspective on
how the bilingual memory organization can change as function of increasing proficiency (see Chapter 1).
To summarize, the age at which a second language is acquired as well as the level of proficiency acquired in a second language can raise many interesting questions regarding the representation and processing of multiple languages in the brain. In the next section, we focus on the role of script in bilingual word recognition and production and review several behavioural studies concentrating on cross-linguistic influences in same-script and different-script bilinguals.