L ITERATURE R EVIEW
2.4 Research on Processing
2.4.2 Asymmetry in Language Processing
In the bilingual lexical processing literature, another controversial issue is the existence of a well-known asymmetry. The fact that processing in the backward direction (i.e., from L2−L1) is performed faster than processing in the forward direction (i.e., from L1−L2) is referred to as asymmetry or directionality effect. A number of findings from cross-language priming studies have provided consistent evidence for an asymmetry in which priming effects were observed only in the forward direction and not in the backward direction. For example, using a stimulus onset asynchrony (SOA) of 200 ms, Altarriba (1992) observed translation priming effects only in the L1−L2 direction. In 1994, Keatley, Spinks, and de Gelder tested
Chinese−English and French−Dutch bilinguals using prime-target pairs that were associatively related and observed unmasked and masked priming effects only when the direction was from L1−L2. Using Hebrew−English bilinguals and stimuli consisting of both cognates and non-cognates, Gollan, Forster, and Frost (1997) observed translation priming only in the L1−L2 direction, irrespective of the cognate status of the word. Jiang (1999) observed that when the translation direction was from L1−L2, translation priming effects were significant, whereas in the opposite direction, i.e., L2−L1, translation priming effects were weak or absent (see Chapter 4 for more details). The review of the research concerning the asymmetry in lexical processing presented in this chapter clearly delineates two crucial issues influencing the phenomenon, namely the application of either the conceptual or the lexical processing route and the word type effect which are discussed in the next section.
2.4.2.1 Processing Route
There is general consensus in the literature that forward processing involves the conceptual route, whereas, backward processing involves the lexical route (Kroll &
Sholl, 1992; Kroll, 1993; Sholl, Sankaranarayanan, & Kroll, 1995). Moreover, depending on second language proficiency level of bilinguals, the direction of processing route is subject to change, which in turn, results in asymmetry. Although many models and theories have been proposed to explain the asymmetry, none of them are completely satisfactory. Perhaps the most popular model that provides a proper explanation to asymmetry in bilingual processing is the Revised Hierarchical Model which suggests that the asymmetry results from a fundamental difference in the mental representations of L1 and L2. Primary evidence in support of this model comes from word translation studies. The model also provides explanation to asymmetrical priming effects often observed in lexical decision tasks. The model proposes that the presence of significant priming effect in the L1−L2 direction is the result of strong connection between L1 lexical representation and conceptual representation, whereas the absence of priming effects in the L2−L1 direction is the
result of weak connection between L2 lexical representations and conceptual representations. However, the model fails to explain the symmetric priming effects observed in semantic categorization tasks.
A second model trying to account for the asymmetry in bilingual processing was the Separate Memory Systems Account proposed by Jiang and Forster (2001).
According to them, bilingual memory consists of two separate memory systems which results in asymmetrical processing. Evidence for this model comes from an
“old-new” episodic recognition task in which they tested Chinese−English bilinguals. The task was to memorize a list of words in their first language and then they were shown a new list of target words which were preceded by its translation equivalent as the masked prime. They were then were asked to determine if the target words were in the original list. The results of the experiments showed masked priming only in the L2−L1 direction, which stands in stark contrast to the findings in lexical decision task where no such priming was observed. They attributed their findings by proposing that L1 and L2 words are stored in two different memory accounts—L1 words in lexical memory and L2 words in episodic memory. As a result of this, masked priming was observed in the “old-new” task because it involves episodic memory, and thereby, L2 primes could facilitate L1 targets, whereas, no priming was observed in lexical decision task which involves lexical memory, and thereby, L2 primes could not facilitate L1 targets. Although the Separate Memory Systems Account explains the priming difference between “old- new” task and lexical decision task, it shares similar weakness to the RHM in that, it fails in providing explanation to the task differences between lexical decision task and semantic categorization task.
A third model which attempted to account for the task differences in lexical decision task and semantic categorization task was the Sense Model proposed by Finkbeiner et al. (2004). According to this model, the absence of priming effect in L2−L1 direction in lexical decision task can be attributed to the fact that a bilingual speaker is familiar with considerably fewer senses associated with L2 words than with L1 words.
Another hypothesis providing tempting explanation to the bilingual processing asymmetry is the Language Mode Hypothesis by Soares and Grosjean (1984) and Grosjean (1992) which proposes that the language mode of a task is responsible for the asymmetry. The model draws its evidence from masked priming studies suggesting that the language of target is the immediate language in use in a masked priming experiment, where a participant is not consciously aware of the prime. As a result of this, a bilingual mode is employed in the L1−L2 direction, and since both languages are activated, the processing of L2 words is facilitated. On the other hand, a monolingual mode is employed in the L2−L1 direction, which activates only the L1, and therefore, the processing of L1 words is not facilitated by L2 primes.
However, the explanation provided by this hypothesis is contradicted by the findings of Jiang (1999), were Chinese−English bilinguals were being prompted to adopt a bilingual mode for a task. The stimuli consisted of Chinese and English target words presented in a random mixed order, so as to avoid the prediction of the target language. Surprisingly, no priming effects were observed in the L2−L1 direction, even with this design which puts the explanation provided by the Language Mode Hypothesis into question. In addition to the factor discussed above, asymmetry in language processing can also be an outcome of the divergences in processing of different types of words to which we shall turn in the following section.
2.4.2.2 The Word Type Effect
The asymmetry in lexical processing is also dependent on the type of words which are being processed, as it has been observed that different types of words can either slow down or speed up lexical processing. This phenomenon is referred to as the word type effect in scientific literature. Word type can be characterized by different variables such as cognateness, concreteness, frequency, etc. (De Groot, 1993; De Groot et al., 1994; De Groot & Comjis, 1995). Since one of the crucial areas of
interest of the present study is the cognate status of the words/pictures, we will only review literature on this particular variable in the following section.
De Groot et al. (1994) conducted forward and backward word translation tasks in order to assess the role of cognateness in lexical processing. The stimuli consisted of both cognate and non-cognate words. They observed that response times for cognates were similar in both forward and backward direction. In contrast, non- cognates were responded to faster in the backward direction. Further, the speed of cognate translation was comparable to the speed of backward non-cognate translation, indicating the use of the same processing route in cognate translation and backward non-cognate translation. Following the predictions of the RHM, cognate processing (both forward and backward) can thus be assumed to proceed via the lexical route since lexical processing in backward direction is generally said to proceed via the lexical route. De Groot et al. (1994) further investigated the processing of cognates using variables such as imageability, context availability and definition accuracy in a translation production task. They observed that forward direction is highly influenced by semantic variables as opposed to backward direction which confirmed that the processing of cognates mainly engages the lexical route regardless of the processing direction. In subsequent experiments using the translation recognition task, De Groot and Comjis (1995) confirmed the stipulations described above.
Several models of bilingual mental lexicon give explanation on how different types of words affect the processing of language. One of such models is the DCF model by De Groot and colleagues (De Groot, 1992a, 1992b, 1993; De Groot et al., 1994;
Van Hell &De Groot, 1998a, 1998b). According to this model, the phenomenon that cognates are processed faster than non-cognates is because of shared conceptual and lexical representation across languages in case of cognates. The word type effect is also explainable within the boundaries of the Mixed Memory Model of bilingual memory proposed by De Groot, 1992b; De Groot & Nas (1991), in line with the hierarchical models. However, this model assumes that the various connections between the lexical and conceptual level is dependent on the type of words being processed and not on the direction of processing.