Two Words, One Meaning: Evidence of Automatic Co-Activation of Translation Equivalents

Dimitropoulou, Maria; Duñabeitia, Jon Andoni; Carreiras, Manuel

doi:10.3389/fpsyg.2011.00188

ORIGINAL RESEARCH article

Front. Psychol., 15 August 2011

Sec. Psychology of Language

volume 2 - 2011 | https://doi.org/10.3389/fpsyg.2011.00188

This article is part of the Research Topic Neurobilingualism: How brain function informs bilingual functioning and vice versa. View all 7 articles

Two words, one meaning: evidence of automatic co-activation of translation equivalents

Maria Dimitropoulou^1,2*

Jon Andoni Duñabeitia¹

Manuel Carreiras^1,3,4

¹ Basque Center on Cognition, Brain and Language, Donostia, Spain
² Departamento de Psicología Cognitiva, Social y Organizacional, Universidad de La Laguna, Tenerife, Spain
³ IKERBASQUE Basque Foundation for Science, Bilbao, Spain
⁴ Departamento de Filología Vasca, Universidad del País Vasco/ Euskal Herriko Unibertsitatea, Bilbao, Spain

Research on the processing of translations offers important insights on how bilinguals negotiate the representation of words from two languages in one mind and one brain. Evidence so far has shown that translation equivalents effectively activate each other as well as their shared concept even when translations lack of any formal overlap (i.e., non-cognates) and even when one of them is presented subliminally, namely under masked priming conditions. In the lexical decision studies testing masked translation priming effects with unbalanced bilinguals a remarkably stable pattern emerges: larger effects in the dominant (L1) to the non-dominant (L2) translation direction, than vice versa. Interestingly, this asymmetry vanishes when simultaneous and balanced bilinguals are tested, suggesting that the linguistic profile of the bilinguals could be determining the pattern of cross-language lexico-semantic activation across the L2 learning trajectory. The present study aims to detect whether L2 proficiency is the critical variable rendering the otherwise asymmetric cross-language activation of translations obtained in the lexical decision task into symmetric. Non-cognate masked translation priming effects were examined with three groups of Greek (L1)–English (L2) unbalanced bilinguals, differing exclusively at their level of L2 proficiency. Although increased L2 proficiency led to improved overall L2 performance, masked translation priming effects were virtually identical across the three groups, yielding in all cases significant but asymmetric effects (i.e., larger effects in the L1 → L2 than in the L2 → L1 translation direction). These findings show that proficiency does not modulate masked translation priming effects at intermediate levels, and that a native-like level of L2 proficiency is needed for symmetric effects to emerge. They furthermore, pose important constraints on the operation of the mechanisms underlying the development of cross-language lexico-semantic links.

Introduction

The learning of a non-dominant second language (L2) by associating a newly learnt word to its translation equivalent in the dominant native language (L1) represents the most common L2 teaching strategy (e.g., Jiang and Forster, 2001; Kroll and Tokowicz, 2005; Comesaña et al., 2009). However, as the proficiency level of the bilinguals increases the need to refer to the L1 to communicate in the L2 decreases (Kroll et al., 2002). In other words, the gradual L2 acquisition leads to gradually enhanced autonomy of this language. This progressive independence of the L2 could be reflected in the way L2 words are processed and represented in relationship to both their L1 translations and their corresponding conceptual representations. The current study reviews the existing evidence of automatic co-activation of translation equivalents gathered using the masked translation priming paradigm and empirically addresses the issue of whether the level of L2 proficiency affects masked translation priming effects. This way, we aim at testing whether at different stages of the L2 acquisition process, when the representational status of the L2 with respect to the L1 differs, the patterns of automatic co-activation of translation equivalents vary.

In order to examine the representational status of translation pairs and the extent to which their conceptual overlap leads to their automatic co-activation, numerous studies have used a version of the masked priming paradigm (Forster and Davis, 1984), the masked translation priming. In this paradigm a pattern mask is first presented for 500 ms followed by the brief presentation of a lowercase prime (∼50 ms) which can be either the translation or a word of the same language unrelated to the immediately following uppercase target word (e.g., casa-HOUSE vs. rueda-HOUSE, casa, and rueda are the Spanish words for house and wheel). The great advantage of this paradigm lies in the masking of the prime, which makes participants unaware of its presence (see Kinoshita and Lupker, 2003, for review).

Masked Priming Evidence on Translation Processing

Following the masked priming procedure, with some small variations in the sequence and timing of the events, almost 20 studies in the last two decades have reported what has been termed as the masked translation priming effect: faster responses to the targets when they are preceded by their translation than by an unrelated word of the non-target language (see Duñabeitia et al., 2010a, for a recent review). This masked translation priming effect has been proposed to result from the automatic activation of the common conceptual node between prime and target and from the existence of strong cross-language interactions at the lexical level (see Forster and Jiang, 2001), although it is also modulated by the sublexical overlap between translations (i.e., larger effects with cognates, e.g., guitar and its Spanish translation guitarra, as compared to non-cognates, e.g., house and its Spanish translation casa; e.g., Gollan et al., 1997; Voga and Grainger, 2007; Davis et al., 2010; Duñabeitia et al., 2010a; but see Kim and Davis, 2003). However, the vast majority of masked translation priming studies has focused on the processing of non-cognates translations, tapping exclusively on lexico-semantic levels of representations due to the lack of any sublexical overlap between them. The essentially semantic origins of the non-cognate masked translation priming effects have been also confirmed in a number of electrophysiological studies reporting more negative-going waveforms for unrelated primes as compared to translation primes in the N400 time-window, reflecting a facilitation of the semantic processing of the targets preceded by their translation primes (Midgley et al., 2009; Duñabeitia et al., 2010a; Hoshino et al., 2010; Schoonbaert et al., 2010).

A remarkable finding in this domain is the so-called non-cognate masked translation priming asymmetry: different magnitude of effects across the two translation directions (i.e., forward, with L1 primes and L2 targets, or backward, with L2 primes and L1 targets) suggesting that fast and automatic lexico-semantic interactions are greatly affected by the readers’ knowledge of the language of the input stimuli. The first report of the masked translation priming asymmetry was obtained in the lexical decision task by Gollan et al. (1997), who found large forward and null backward masked translation priming effects. However, asymmetric effects in the opposite direction have been also found in the episodic old–new recognition task (e.g., Jiang and Forster, 2001; Finkbeiner, 2005). Interestingly, this asymmetric representational status of L1 and L2 items is only captured in tasks without an explicit semantic component, whereas when participants are overtly instructed to semantically process the stimuli the effects are comparable across the two translation directions (i.e., semantic categorization task; Grainger and Frenck-Mestre, 1998; Finkbeiner et al., 2004; Wang and Forster, 2010).

While the task-dependency of the masked translation priming asymmetry has implications in understanding the exact nature of the asymmetry(see Jiang and Forster, 2001, for discussion), the extensive use of the lexical decision task in monolingual and bilingual psycholinguistic research and the fact that the masked translation priming asymmetry was first obtained in this task has led the vast majority of non-cognate masked translation priming studies to use this task, with most of them replicating the initially reported asymmetry (i.e., larger effects in the L1 → L2 translation direction, than vice versa; see Table 1 for an overview of the lexical decision non-cognate masked translation priming literature). In further detail, out of 16 studies, 13 have found robust masked translation priming effects with L1 primes and L2 targets (i.e., forward translation; a mean effect of 41 ms across 21 experiments), while only seven studies have found such an effect with L2 primes and L1 targets (i.e., backward translation; a mean advantage of 9 ms). In fact, even in the cases where there was a numerical effect in the L2 → L1 translation direction, this is usually smaller than in the L1 → L2 direction (in 10 out of the 13 studies testing both translation directions) and sometimes non-significant (11 experiments out of 19 testing this translation direction). The same asymmetric pattern reported in the lexical decision latencies has been also confirmed by electrophysiological findings with N400 non-cognate masked translation priming effects being mostly evident in the forward and less in the backward translation direction (but see Duñabeitia et al., 2010b; see also Nakamura et al., 2010, for an fMRI replication).

TABLE 1

Table 1. Description of the published lexical decision studies testing non-cognate masked translation priming effects and of the reported characteristics of the bilinguals tested.

This asymmetric pattern of masked translation priming effects found in reaction times and neuroimaging studies could seem initially surprising given that one would expect that the effects would be unaffected by the translation direction. However, it becomes much easier to accommodate these findings by considering that all the studies reporting asymmetric masked translation priming effects have tested bilinguals who were clearly less proficient in their L2 than in their L1, namely unbalanced bilinguals (see Table 1 and Duñabeitia et al., 2010b, for a review of the ERP studies). Thus, suggesting that processing differences between words of the dominant and the non-dominant languages would lead to this directional asymmetry. This explanation of the asymmetry would therefore lead to the prediction that when this representational L1–L2 imbalance is attenuated or eliminated, namely with very highly proficient native-like bilinguals or with bilinguals without a clear L1 preference (i.e., balanced), the asymmetry should vanish. In support of this proposal, Basnight-Brown and Altarriba (2007) found symmetric effects with very highly proficient Spanish–English¹ bilinguals who had undergone a language dominance shift. The fact that they had even reported being more competent in the language they acquired later as compared to their native language could have led to this symmetric pattern of effects. Even stronger evidence in this line, was recently reported by Duñabeitia et al. (2010a) testing balanced Basque–Spanish bilinguals who were constantly exposed to both of their languages. The authors found significant and symmetric bi-directional effects, which were also replicated in an ERP study with bilinguals of the same characteristics (Duñabeitia et al., 2010b). The only evidence so far against a critical involvement of the level of L2 proficiency in the pattern of masked translation priming effects has been reported with a group of low proficient Dutch–French bilinguals yielding significant effects in both translation directions (Duyck and Warlop, 2009).Surprisingly, in spite of their large numerical difference (22 ms) these effects were not significantly different from each other. Nevertheless, in the light of this unexpected symmetry the authors suggested that a potential lack of statistical power could be leading to these results. In fact, in another study testing two groups of Greek–Spanish bilinguals of a comparable low-level of L2 proficiency (Dimitropoulou et al., 2011a) asymmetric effects, significant only in the L1 → L2 translation, were found, fully replicating the previously established asymmetry reported with unbalanced bilinguals. Crucially, the asymmetry persisted even when participants were provided with 50 ms extra time to process the primes, exactly mimicking the procedure followed by Duyck and Warlop (2009). In the light of the general pattern of effects obtained across the different studies it becomes feasible to assume that the level of L2 competence is the critical factor driving the pattern of masked translation priming effects.

Effects of L2 Proficiency on Lexico-semantic Processing

The assumption that masked translation priming effects could be influenced by the level of L2 proficiency is further supported by evidence pointing to a critical role of this factor in the lexico-semantic processing of L2 and in the extent to which this is comparable to that of the dominant language (e.g., Leonard et al., 2011). Several studies have shown that although less proficient bilinguals can directly access the meaning of L2 words, they perform worse than more proficient bilinguals in tasks requiring the lexico-semantic activation of L2 items (e.g., Chen and Leung, 1989; Chee et al., 2001; Sunderman and Kroll, 2006; see Kroll et al., 2010; Van Heuven and Dijkstra, 2010, for recent reviews). Favreau and Segalowitz (1983) showed that at brief stimulus-onset asynchronies (SOAs) highly proficient bilinguals showed greater semantic priming than less proficient bilinguals when reading in their L2. Using the masked priming paradigm several studies have reported different cross-language associative/semantic effects with bilinguals of different levels of L2 proficiency. Testing relatively high proficient unbalanced bilinguals Schoonbaert et al. (2009) obtained significant bi-directional effects which were however larger in the L1 → L2 priming direction (see also Duyck, 2005). Similar to what has been reported in the non-cognate masked translation priming literature, this directional asymmetry is eliminated with balanced native bilinguals, with bi-directional and symmetric associative/semantic effects emerging (Perea et al., 2008; but see Basnight-Brown and Altarriba, 2007). Even more relevant for the purposes of the present study is the evidence showing different effects at different levels of L2 proficiency in tasks involving the processing of translation equivalents. Kroll et al. (2002) found that unbalanced bilinguals were faster in producing the L1 translation of an L2 word, than vice versa and that this asymmetry was smaller with a more proficient but still unbalanced group (see also Alvarez et al., 2003; Christoffels et al., 2006). In the comprehension domain, it has been shown that the performance of low proficient bilinguals is more sensitive to the resemblance of L2 words to their L1 translation and less to their semantic overlap, while the opposite is true for more competent groups of bilinguals and that when processing L2 words the activation of the L1 translation becomes less pronounced when L2 proficiency increases (e.g., Talamas et al., 1999; Elston-Güttler et al., 2005; Ferré et al., 2006; Sunderman and Kroll, 2006; but see De Groot and Poot, 1997; Thierry and Wu, 2007). To sum up, three relatively consistent findings reported across the bilingual literature are that: (i) early in the L2 acquisition process L2 lexico-semantic access seems to be more effortful than later on, (ii) at this stage the reliance on the activation of the L1 translation equivalent is larger and, (iii) as the L2 proficiency level increases, asymmetries in the processing of L1 and L2 words are attenuated.

Theoretical Accounts of Mental Translation across the L2 Proficiency Span

Accounting for the set of findings pointing to a critical role of L2 proficiency in the representational status of the two languages of bilinguals has been one of the core aims of most models of bilingual lexico-semantic organization (see French and Jacquet, 2004; Grainger et al., 2010; for reviews). Kroll and colleagues developed a theoretical account explicitly designed to account for the processing of translation equivalents at different levels of L2 proficiency during language production: the revised hierarchical model (RHM; e.g., Kroll and Stewart, 1994; Kroll and Tokowicz, 2001, 2005). In its most recent version, the RHM posits that L1 and L2 words are stored in functionally separate lexicons that are linked to a common semantic/conceptual store. Critically, the progressive increase in L2 proficiency is reflected in the strengthening of the links of L2 words to their corresponding concepts and the weakening of their links to their L1 equivalent lexical item. Due to this pattern of lexico-semantic connections, low proficient bilinguals need to activate the L1 translation equivalent to retrieve the corresponding L2 word, while at the same time they are slower at accessing the meaning of L2 words as compared to that of L1 words (see Kroll et al., 2010). As the level of L2 proficiency increases the lexical and semantic connections of L2 words become gradually more comparable to those of L1 words, up to the extent of becoming symmetrical, when bilinguals reach the highest levels of L2 proficiency. With regard to the non-cognate masked translation priming asymmetry Kroll and colleagues proposed that when testing unbalanced bilinguals the semantic activation would be more effective with L1 primes as compared to L2 primes due to the stronger links between L1 words and concepts, hence leading to larger masked translation priming effects (Kroll and de Groot, 1997; Kroll and Tokowicz, 2001). Following the model’s central assumption of a progressively more symmetric pattern of L1 and L2 lexico-semantic links as a matter of increased L2 proficiency, the RHM would predict that the masked translation priming asymmetry would be gradually attenuated as the level of L2 competence would increase and eventually eliminated with balanced native-like bilinguals (e.g., Duñabeitia et al., 2010a,b).

Similar predictions regarding the modulation of masked translation priming effects as bilinguals become more proficient in their non-dominant language are also made by the Bilingual Interactive Activation models (BIA and BIA+; e.g., Dijkstra and van Heuven, 1998, 2002; Van Heuven et al., 1998). Masked translation priming effects and their potential modulation by the level of L2 proficiency offer an ideal experimental setting for testing the validity of the BIA models since these models were designed to account for the bilingual visual word recognition findings and they have effectively simulated masked priming effects of cross-language lexico-semantic activation across different levels of L2 proficiency (e.g., Dijkstra and van Heuven, 1998, 2002).The BIA models, which operate based on the same principles as their predecessor, the Interactive Activation model of monolingual visual word recognition (McClelland and Rumelhart, 1981), propose that words of both languages are stored in a single unified lexicon, thus accounting for the cross-language lexico-semantic interactions repeatedly reported. According to the BIA framework, processing asymmetries between L1 and L2 words observed with unbalanced bilinguals are caused by differences in their relative frequency and/or recency of use of L1 and L2 words. For this type of bilingual, L2 words are generally encountered less frequently than L1 words leading to lower resting levels of activation and costlier recognition than for L1 items. However, as the L2 proficiency level increases and bilinguals become more exposed to L2 words, their activation thresholds decrease and they become more easily accessed. As a consequence, their recognition becomes more similar to that of L1 words. Within the context of the masked translation priming, this progressive increase in the times a bilingual encounters L2 words is proposed to be reflected in the ease with which the L2 masked primes get activated and activate their corresponding semantic nodes. At higher levels of L2 proficiency, when the L2 primes are the translation equivalents of the targets the pre-activation of the shared meaning would facilitate the processing of the target, thus gradually assimilating the effects obtained with L1 primes and L2 targets.

Very recently, the developmental BIA-d model (Grainger et al., 2010), a new theoretical approach combining some of the critical functional principles of the RHM and the BIA models has been put forward. The BIA-d model was designed to account for the findings revealing changes in L2 lexico-semantic access and L1–L2 interactions throughout the L2 proficiency span. In this framework, initially the newly learnt L2 words are connected via excitatory connections to their L1 translation as well as to their corresponding meaning. These connections are strengthened with increased exposure via Hebbian learning mechanisms, based on the structure and premises of the RHM’s developmental account. However, as the L2 proficiency increases and bilinguals reach “a magic moment” in the L2 acquisition, L2 words become integrated into the L1 lexicon and their recognition proceeds in the frequency-dependent way proposed by the BIA models. The BIA-d posits that at this point the strength of the connections between translation equivalents starts to decrease and the top-down inhibitory control of language activation becomes more effective, thus leading to a more autonomous L2 processing. With regard to the non-cognate masked translation priming effects, the BIA-d model proposes that they reflect ease of direct semantic access of the test items, hence fore explaining the asymmetries observed in unbalanced bilinguals in a way similar to that of the RHM. Accordingly, since throughout the proficiency continuum the excitatory connections of L2 words to their meaning become gradually stronger, thus more comparable to those of L1 words, the BIA-d would predict that as L2 proficiency increases, the masked translation priming asymmetry should be gradually attenuated.

Masked Translation Priming and L2 Proficiency

As can be appreciated, in line with previous evidence and according the predictions offered by some of the most cited bilingual models, the bilinguals’ level of L2 proficiency would be expected to modulate non-cognate masked translation priming effects. Nevertheless, this has not been yet examined. A potential reason for this could be that most studies have opted for testing relatively high proficient unbalanced bilinguals with a college-level knowledge of their L2 to partly ensure the effective processing of L2 items. Critically, even when considering the small number of studies intentionally focusing on specific levels of L2 proficiency (low or native-like) to extract the pattern of masked translation priming effects obtained across different levels of L2 proficiency, the existence of a number of issues make it hard to draw reliable cross-study conclusions. The most important limitation involves the diverse and sometimes underspecified linguistic history of the bilinguals tested. This results partly from the exclusive use of either objective or subjective measures of L2 proficiency by some authors (e.g., Jiang, 1999; Jiang and Forster, 2001; Duyck and Warlop, 2009; Schoonbaert et al., 2009) and from the scarce descriptions of the linguistic history of the bilinguals (e.g., Grainger and Frenck-Mestre, 1998; Kim and Davis, 2003). These rather rough descriptions reveal that even when the bilinguals tested had indeed a uniform level of L2 proficiency, their age of L2 acquisition or the context in which L2 was acquired were underspecified. On top of these potentially confounded variables, the great variability in the sizes of the bilingual samples tested (ranging from 3 to 52) as well as in the number of experimental items presented (ranging from 9 to 60 items per priming condition) could be influencing the pattern of effects obtained due to statistical power differences. Finally, only a small number of studies have opted for testing twice the same bilinguals (e.g., Duyck and Warlop, 2009; Duñabeitia et al., 2010a; Dimitropoulou et al., 2011a). The between subject designs add a considerable amount of variance in the response latencies which could be further influencing the pattern of the effects obtained across the two translation directions.

The second crucial limitation in establishing the pattern of masked translation priming effects at different levels of L2 proficiency is the different language combinations examined each time. As shown in Table 1, a large number of studies have used combinations of Romance languages (e.g., Spanish–English, Dutch–English, Dutch–French, etc.) with almost completely overlapping graphemes and phonemes as well as partly overlapping lexicons (i.e., large number of cognates). Two studies have combined partly overlapping scripts (Greek and Roman) while others have used languages involving completely distinct alphabets (Hebrew and Roman) or even different writing systems (logographic and alphabetic). The potential influence of the script and language combinations used in the effects obtained across the different lexical decision non-cognate masked translation priming studies can be appreciated in the effects reported so far in the L2 → L1 direction. Critically, all the studies that have shown significant L2 → L1 masked translation priming effects have examined languages with a common alphabet. This seems to be somewhat unexpected since the script change present in the cross-language priming conditions of cross-script studies could be thought to facilitate the activation of the non-target language by providing a low-level visual cue of its presence in the task. Furthermore, although testing languages with a common script mostly yields to significant translation effects, the Spanish–English language combination is surprisingly unique since it has only led to null non-cognate masked translation priming effects (e.g., Sánchez-Casas et al., 1992; Davis et al., 2010), though yielding to significant effects with cognates or even with non-cognates when either Spanish or English are combined with other languages (e.g., Schoonbaert et al., 2009; Duñabeitia et al., 2010a). Due to these inconsistencies, whether examining same or different scripts modulates the effects is still an issue under discussion (see Gollan et al., 1997; Hoshino et al., 2010).

Finally, the masked priming methodology used each time could have been also affecting the effects caused by the level of L2 proficiency of the bilinguals. It is noteworthy that significant masked translation priming L2 → L1 effects have mostly emerged in studies using SOAs longer than 50 ms (see Table 1). Schoonbaert et al. (2010) have recently obtained significant bi-directional behavioral and N400 effects with high proficient unbalanced bilinguals by presenting the prime for 100 ms (see also Basnight-Brown and Altarriba, 2007). In the light of their results the authors concluded that “increasing participants’ proficiency in L2 or increasing prime–target SOA can be thought of as having the same influence on the amount of processing of briefly presented L2 prime words” (p. 6). However, two studies have tested and rejected the hypothesis that having extra time for processing the L2 prime by including a blank or a post-mask facilitates the appearance of the otherwise elusive backward masked translation priming effect (Jiang, 1999; Dimitropoulou et al., 2011a). This idea is further supported by the appearance of significant within-language L2 repetition priming effects and of significant backward masked translation priming effects in tasks other than the lexical decision (e.g., Gollan et al., 1997; Finkbeiner et al., 2004).

The Present Study

In order to empirically address the issue of whether L2 proficiency modulates non-cognate masked translation priming effects we conducted three lexical decision experiments, carefully designed to overcome the limitations previously enumerated. Throughout this series of experiments all the variables proposed to influence non-cognate masked translation priming effects were kept constant and we exclusively manipulated the level of L2 proficiency of the participants. In further detail, after a thorough selection process (see Participant Selection) 108 Greek–English unbalanced bilinguals were assigned to one of three proficiency groups: a relatively low, a medium, and a relatively high proficiency group. Our biggest effort was placed in establishing a clear L2 proficiency distinction across the three groups, based on both subjective and objective measures, and in ensuring that the L2 history of the three groups was otherwise identical. The L2 proficiency manipulation was focused on unbalanced bilingualism since the evidence of symmetric masked translation priming effects across the two translation directions with balanced bilinguals has been confirmed both at the behavioral and at the electrophysiological level (Duñabeitia et al., 2010a,b). To examine the pattern of masked translation priming effects emerging across both translation directions as well as the relationship between them (i.e., asymmetry) while eliminating any between subject variability, each group of bilinguals was tested twice using the exact same large sets of English and Greek materials in two separate experimental sessions. The critical translation pairs used to test both translation directions were frequent one-to-one non-cognate Greek–English translations (e.g., ribbon and its Greek translation κoρδε′λα), thus ensuring that even the low proficient bilinguals would be familiar with the English items. Finally, to further refine the experimental design, for each target language we added a within-language repetition priming condition along with its corresponding within-language control (i.e., identity priming effect, e.g., ribbon-RIBBON vs. desire-RIBBON; e.g., Forster and Davis, 1984; Perea and Rosa, 2000). The use of a within-language full priming condition against which cross-language effects can be compared provides valuable insights into the representational relationship of L1 and L2 words (see Altarriba and Basnight-Brown, 2007). This is more so when testing low proficient bilinguals, since obtaining significant L2 identity priming effects certifies the effective lexical activation of the less frequently encountered L2 words (see also Dimitropoulou et al., 2011a; Gollan et al., 1997; Jiang, 1999; Midgley et al., 2009; for the same 2 × 2 design applied in the study of masked translation priming effects).

Overall, we expected to observe a gradually improved performance in English (L2) as a matter of increased proficiency, with progressively shorter latencies and fewer errors from low to medium and to high proficient bilinguals (see De Groot and Poot, 1997). With regard to the masked identity priming effects we expected to obtain significant effects (i.e., shorter latencies for targets primed by their exact repetition than for targets primed by unrelated words of the same language) of comparable magnitude in L1 and in L2 across the three L2 proficiency levels (e.g., Gollan et al., 1997; Dimitropoulou et al., 2011a). Furthermore, considering previous L2 masked priming studies, showing invariant morphological or form priming effects across different levels of proficiency, we did not predict any modulation in the size of the L2 masked identity priming effect across the three groups of bilinguals (see also Duyck et al., 2004; Diependaele et al., 2011; Dimitropoulou et al., 2011b).

Regarding the effects of major interest, the non-cognate masked translation priming effects, we expected to obtain significant forward masked translation priming effects for the three proficiency groups (Experiments 1a, 2a, and 3a), as has been typically the case in the lexical decision masked translation priming literature irrespectively of the level of L2 proficiency of the bilinguals tested (see Table 1, for review). Predictions on whether or not we would also obtain an effect in the opposite translation direction are less clear-cut given the inconsistent previous evidence (see above). Following different rationales, the RHM and the BIA models would predict that such an effect could potentially exist at high levels of L2 proficiency, when the processing of L2 words is more comparable to that of L1 words (see Dijkstra, 2007). If the models’ predictions regarding the appearance of the L2 → L1 effect at high L2 proficiency levels are confirmed and there is indeed such an effect with the high proficiency group (Experiment 3b), then it could also be expected that for this group this effect could be of comparable magnitude to that of the L1 → L2 masked translation priming effect. If, in contrast to the predictions of the RHM and the BIA models, the level of L2 proficiency of an unbalanced bilingual does not affect the L2 → L1 masked translation priming effect, then asymmetric effects across the two translation directions (i.e., larger effects in forward as compared to backward translation) should be expected for the three proficiency groups.

Finally, the inclusion of equal amount of primes belonging to the target and non-target languages preceding the English (L2) and the Greek (L1) targets as well as the substantial statistical power of our design offer a great opportunity to investigate an effect widely neglected in the behavioral masked priming literature: the masked priming code-switching effect. Code-switching costs have been manifested mostly in word production but also in some recent ERP masked priming reading studies as costlier processing of pictures or words preceded by an item of the non-target language as compared to when they were preceded by items of the same language (e.g., Costa et al., 2006; Chauncey et al., 2008, for review). Out of these studies, the ones testing unbalanced bilinguals have reported a dependence of the code-switching effects on the direction of the code-switch (larger cost from L2 → L1, than vice versa), while those testing balanced bilinguals have reported symmetric effects (e.g., Costa et al., 2006; Duñabeitia et al., 2010b). However, the only behavioral masked priming studies examining code-switching costs reported symmetric effects even though one tested low proficient unbalanced and the other native-like balanced bilinguals (Perea et al., 2008; Dimitropoulou et al., 2011a). Taking into account these previous behavioral masked priming reports of code-switching effect, we expected to obtain symmetric effects across the two directions of language switch for the three groups of bilinguals tested.

Experiments

Method

Participant selection

To ensure the correct assignment of each participant to his/her corresponding L2 proficiency level as well as the homogeneity of each of the groups to be tested, we opted for assessing the L2 proficiency with both objective and subjective measures. In order to obtain an objective measurement of their proficiency, all the native Greeks comprising the three groups were English learners of different levels at the British Council in Athens. This way apart from making sure that all the bilinguals were exposed to the same type of English input, we were able to identify three distinct levels of English proficiency based on the placement of the bilinguals in three different English courses according to the British Council standards: relatively low, medium, and high proficiency groups. This grouping was made based on thorough spoken and written entry tests as well as on the participants’ academic progress in the British Council. The entry tests were administered upon students’ first registration and consisted of a written (vocabulary, grammar, and comprehension subtests) and a spoken part. The spoken part of the test was a brief interview during which each student was evaluated on his/her communication skills in English through their answers on a series of open questions. Based on these measures the British Council teaching team indicated that the most clear-cut proficiency distinction was found across the students who were in the process of undertaking one of the three available ESOL Examinations supervised by the University of Cambridge: the First Certificate in English (FCE), the Certificate of Advanced English (CAE), and the Certificate of Proficiency in English (CPE). Once the groups had been identified following the British Council standards, the subjective criterion was applied. The prospective participants answered a number of questions regarding their linguistic and educational background and gave their self-ratings on different measures of proficiency in English by completing a Greek version of the Language Experience and Proficiency Questionnaire (LEAP-Q; Marian et al., 2007). This questionnaire confirmed that all the participants had only lived in Greece, that English was their second language both in terms of proficiency and in order of acquisition and that they were exposed to it only within the context of the British Council. The three proficiency groups were furthermore matched in a number of different variables (mean age of acquisition, age of first exposure to print, chronological age; see Table 2 for a detailed description of the three groups of bilinguals).

TABLE 2

Table 2. Characteristics of the three groups who participated in the experiments and their mean level of English (L2) proficiency as calculated by their self-ratings (Language Experience and Proficiency Questionnaire, LEAP-Q) and by the British Council entry tests.

Materials

Exactly the same experimental materials were used in the three experiments (1–3). For sub-experiments 1a, 2a, and 3a we selected 232 English (L2) as word targets (e.g., RIBBON) from the CELEX database (Baayen et al., 1995). These targets were preceded by primes that were: (i) their exact repetition (e.g., ribbon–RIBBON), (ii) an English unrelated word (e.g., desire-RIBBON), (iii) their non-cognate Greek translation equivalent (e.g., κoρδε′λα-RIBBON) or, (iv) a Greek unrelated word (e.g., φυλακη′-RIBBON; φυλακῄ is the Greek word for prison). All the words used throughout the study were nouns or adjectives. All the conditions were matched in mean frequency per million and length. All the Greek words were taken from the GreekLex database (Ktori et al., 2008). The selected English–Greek non-cognate pairs were indicated to be the predominant translations of each other by two Greek external judges with a native-like level of competence in English (see Table 3 for a full description of the materials). For the purposes of the lexical decision an additional set of 232 pronounceable non-words was created by replacing two of the target words’ letters (e.g., GOMY). In order to have the exact same amount of English and Greek primes throughout the experiment, the non-words were preceded half by Greek and half by English prime words, matched in length and frequency to the primes of the word targets (mean frequency: 97 appearances/million, mean length: 6.2 letters).

TABLE 3

Table 3. Characteristics of the word materials used in the experiments.

In Experiments 1b, 2b, and 3b we used as the critical non-cognate translation pairs the same ones as in Experiments 1a–3a, but this time the Greek primes of the translation condition served as targets and the English targets as translation primes. Just as in Experiments 1a–3a with the English targets, the Greek target words were preceded by (i) their exact repetition (e.g., κoρδε′λα-κoρδε′λα), (ii) a Greek unrelated word (e.g., φυλακη′-κoρδε′λα), (iii) their English non-cognate translation (e.g., ribbon-κoρδε′λα), or (iv) an English unrelated word (e.g., desire-κoρδε′λα; see Table 3 for a full description of the word materials). 232 pronounceable non-words were created by replacing two of the targets’ letters (e.g., ΞALI). These non-words were primed by the same Greek and English words that preceded the non-word targets in Experiments 1–3a (see Altarriba and Basnight-Brown, 2007).

For each sub-experiment four lists of materials were created so that each target appeared only once in each list and each time in a different priming condition. In each of the lists there were 58 experimental items per condition. List assignment was counterbalanced across participants.

Procedure

All the participants completed the task in English (Experiments 1a–3a) and in Greek (Experiments 1b–3b) in two experimental sessions. The sessions took place in two different days with at least a 3-day lag between them and their order was counterbalanced across the participants. The experiments were run using DMDX (Forster and Forster, 2003). Each trial started with the presentation of a forward mask (e.g., ######) for 500 ms, followed by the presentation of a lowercase prime for 50 ms (three cycles; each corresponding to 16.6 ms on a CRT monitor). Finally, the target string was presented in uppercase, for a maximum of 2500 ms. All the stimuli were presented centered. Participants were asked to indicate as fast and accurately as possible through a keyboard button press, whether the target string was or not a legitimate English (Experiments 1a–3a) or a legitimate Greek word (Experiments 1b–3b). They were not informed of the presence of the primes, and none of them reported conscious knowledge of their existence after completing the experiments. The order of trial presentation was randomized across participants. Prior to the 464 experimental trials each participant was presented with six word and six non-word practice trials. All the interactions with the participants and the experimental instructions were in the language each participant was performing the task in. Each experimental session lasted approximately 20 min.

Data Analyses

In order to identify the effects produced by each of the three bilingual groups across each translation direction and following previous masked translation priming studies that have used the same design (e.g., Gollan et al., 1997; Dimitropoulou et al., 2011a), ANOVAs based on participant and item response latencies and error percentages were conducted for each group and for each target language. These ANOVAs were based on a 2 (Prime language: English, Greek) × 2(Relatedness: Repetition, Unrelated) × 4(List: List 1, 2, 3, 4) design. The factor List was included as a dummy variable (Pollatsek and Well, 1995). This design led to 12 separate sets of ANOVAs for the reaction times and for the error rates too: one for each of the three bilingual groups (low, medium, high proficiency; Experiments 1–3), one for each of the two translation directions (L1 → L2 and L2 → L1) and one for participant and item analyses. See Tables 3–5 for mean reaction times, error rates, and priming effects obtained in the different priming conditions throughout Experiments 1–3.

Experiment 1: Low Proficiency Group

Participants

Thirty-six native Greeks, students of the British Council who were in the process of undertaking the Cambridge exam of the FCE completed this experiment. According to the University of Cambridge standards English learners in preparation for this examination should be able to understand relatively complex pieces of writing and conversations on a variety of topics and to express their opinion. Based on their performance on the spoken part of the British Council entry tests, participants were able to produce longer sentences using simple grammatical structures in English but their communication was slow and occasionally hesitant and they were not yet able to spontaneously initiate a conversation. In overall, participants rated their English proficiency with a 5.8 on a 1-to-10 scale (10 representing the highest level of proficiency; see Table 2 for further information). Note that in both previous masked translation priming studies testing low proficient bilinguals, participants’ ratings of their overall proficiency were also in the same range (Duyck and Warlop, 2009; Dimitropoulou et al., 2011a). Each participant completed the task with both English and Greek targets (sub-experiments 1a and 1b).

Results and Discussion

English (L2) targets

ANOVAs on the reaction times showed a significant main effect of Prime language: participants responded faster (18 ms) to targets preceded by English repetition and unrelated primes compared to targets preceded by Greek repetition and unrelated primes [a code-switching cost: F1(1,32) = 26.79, MSE = 434, p < 0.001; F2(1,227) = 11.56, MSE = 7818, p < 0.01]. Moreover, the main effect of Relatedness was also significant: participants responded faster (48 ms) to targets preceded by repetition primes (English and Greek) than to targets preceded by English and Greek unrelated primes [F1(1,32) = 166.58, MSE = 489, p < 0.001; F2(1,227) = 126.28, MSE = 4835, p < 0.001]. Importantly, the interaction between the two factors was also significant, indicating that the Identity priming effect was significantly larger than the Translation priming effect [a 34-ms difference; F1(1,32) = 23.45, MSE = 450, p < 0.001; F2(1,227) = 13.05, MSE = 4003, p < 0.001]. The pairwise comparisons showed that responses to targets preceded by their exact English repetition were faster (65 ms faster) than responses to targets preceded by unrelated English words [Identity priming effect: F1(1,32) = 177.86, MSE = 436, p < 0.001; F2(1,227) = 127.70, MSE = 3993, p < 0.001]. Similarly, responses to targets preceded by their Greek non-cognate translations were faster (31 ms faster) than responses to targets preceded by unrelated Greek words [Translation priming effect: F1(1,32) = 33.15, MSE = 503, p < 0.001; F2(1,227) = 8.81, MSE = 3601, p < 0.01].

ANOVAs on the error rates showed a main effect of Relatedness: targets were responded to more accurately (3.3% less errors) when they were primed by repetition primes (English and Greek) as compared to when they were primed by unrelated English and Greek primes [F1(1,32) = 37.82, MSE = 10, p < 0.001; F2(1,228) = 31.04, MSE = 86, p < 0.001]. The rest of the effects did not reach significance (all ps > 0.15).

Greek (l1) targets

ANOVAs on the reaction times showed a main effect of Prime Language, reflecting a 15-ms cost in the trials involving a prime–target language change [F1(1,32) = 20.11, MSE = 396, p < 0.001; F2(1,228) = 10.51, MSE = 5702, p < 0.01]. There was also a main effect of Relatedness, with repetition primes (Greek and English) leading to faster lexical decision times (36 ms faster) than unrelated primes [of both languages; F1(1,32) = 129.53, MSE = 453, p < 0.001; F2(1,228) = 13.49, p < 0.001]. Critically, the interaction between the two factors was also significant showing that the Identity and the Translation priming effects differed in magnitude [F1(1,32) = 27.63, MSE = 412, p < 0.001; F2(1,228) = 36,48, MSE = 2883, p < 0.001]. The pairwise comparisons reveled that, despite their numerical difference (43 ms) both the Identity and the Translation priming effects were significant [Identity priming effect: 57 ms, F1(1,32) = 153.27, MSE = 376, p < 0.001; F2(1,228) = 115.07, MSE = 3263, p < 0.001; Translation priming effect: 14 ms, F1(1,32) = 20.40, MSE = 189, p < 0.001; F2(1,228) = 8.81, MSE = 3601, p < 0.01].

The error rate analysis revealed a significant main effect of Prime Language: targets were responded to 1.2% more accurately when preceded by Greek primes than by English primes [F1(1,32) = 7.29, MSE = 7, p < 0.05; F2(1,228) = 3.97, MSE = 86, p < 0.05]. Furthermore, there was a main effect of Relatedness: participants made 1.5% less errors to targets preceded by their repetitions (either Greek or English) compared to targets preceded by unrelated primes [F1(1,32) = 7.23, MSE = 12, p < 0.05; F2(1,228) = 7.58, MSE = 81, p < 0.01]. The rest of the effects were not significant (all ps > 0.55; see Table 4).

TABLE 4

Table 4. Mean lexical decision times (in ms, RT) and error rates (%E) for word targets in sub-experiments 1a and 1b.

The main finding of Experiment 1 was an asymmetric pattern of non-cognate masked translation priming effects obtained with relatively low proficient Greek–English bilinguals: significant masked translation priming effects were found in both translation directions with a larger effect emerging in the forward translation (31 vs. 14 ms in the backward translation). This asymmetry is in line with the vast majority of previous studies testing unbalanced bilinguals (see Table 1). In contrast to this pattern of translation effects, the code-switching costs observed were unaffected by the prime–target language (i.e., L1 → L2 and L2 → L1 switches lead to symmetric significant costs of 18 and 14 ms, respectively). Similarly, the masked identity priming effects found with Greek (57 ms) and English targets (65 ms) were also comparable in magnitude.

The overall pattern of the different masked priming effects was further confirmed by a set of post hoc combined analyses of the lexical decision latencies of Experiments 1a and 1b in which Target language was included as a factor. With regard to the two translation priming effects these analyses confirmed that the 31-ms forward masked translation priming effect was significantly larger than the 14-ms backward translation as indicated by the significant interaction of Target language and Relatedness found for the between language priming conditions (translation and unrelated) Target language and Relatedness interacted with each other, [F1(1,32) = 6.27, MSE = 359, p < 0.05; F2(1,228) = 5.73, MSE = 3997, p < 0.05]. In contrast, this interaction was not significant when analyzing conjointly the within-language conditions (repetition and unrelated) across Experiments 1a,b (both ps > 0.19) indicating that the 8-ms difference in the within-language repetition priming effects was negligible. Finally, the lack of a directional asymmetry for the two code-switching effects found was confirmed by the absence of an interaction between Target language and Prime language (target, non-target; both ps > 0.55).

In Experiment 2, we used the same materials and procedure to examine the masked translation priming with another group of unbalanced Greek–English bilinguals taken from the same English learning context, who had a higher level of English proficiency, which we termed as medium proficiency. In the light of the results obtained with the low proficient group we expected to find an asymmetric pattern of masked translation priming effects in the presence of significant effects in both translation directions.