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Can adults learn L2 grammar after prolonged exposure under incidental conditions? [1]
['Panagiotis Kenanidis', 'Chair Of Language', 'Cognition', 'Department Of English', 'American Studies', 'Friedrich-Alexander-Universität Erlangen-Nürnberg', 'Erlangen', 'Ewa Dąbrowska', 'Department Of English Language', 'Linguistics']
Date: 2023-08
The current study examined adult learners’ capacity to learn new grammatical rules from incidental exposure. Our main goal was to examine whether adults can learn different aspects of grammar incidentally and the degree to which learning is modulated by their prior L1 experience. In the two experiments presented here, learners with different L1 backgrounds (English and German) were exposed to Kepidalo, a new artificial language that included case marking while allowing for a relatively flexible word order with a canonical SOV and a non-canonical OSV order. Furthermore, in an effort to extend previous literature, we investigated if extensive incidental exposure can lead to higher levels of learning than those reported in previous studies and whether the degree of learners’ conscious knowledge of the grammatical regularities contributed to their learning outcomes.
Learning novel word order and case marking rules through extensive incidental exposure (RQ1, RQ2, & RQ3)
The results of Experiments 1 and 2 showed that, even after extensive incidental exposure to the artificial language, overall, both L1-English and L1-German learners continue to exhibit only partial knowledge of the language’s grammatical rules. These findings appear to align well with previous artificial language studies showing that learning nonnative structures under incidental conditions poses a great challenge for adult learners, leading to generally low learning effects (e.g., [11, 13, 40]).
That is, however, not to say that the learning difficulties observed apply uniformly to all grammatical aspects of the language. Rather, it appears that participants succeed in learning certain aspects of word order. Evidence of this comes from the GJT, where performance on sentences containing verb placement violations was found to be close to ceiling, indicating that participants from both language groups possessed well-developed knowledge of the verb-final rule of the language. This is in accord with the learning outcomes reported by Rebuschat et al. [12] and Walker, Monaghan, Schoetensack, and Rebuschat [110]. We hypothesize that the high accuracy on trials involving verb placement violations observed here can be attributed to a number of factors that work in unison. Firstly, the rigidity of verb placement may have rendered the verb position a consistent and reliable cue to word order, making it more accessible and learnable to participants. Secondly, given that items that appear towards the end of sentences are privileged during sentence processing [111–113], it is likely that the systematic occurrence of verbs in sentence-final position may have increased their overall perceptual salience, making it easier for participants to learn them and, consequently, identify them in the sentence. This allowed learners to notice the erroneous verb placements in the GJT and correctly judged these sentences as ungrammatical. A third factor may relate to the morphological properties of the novel verbs. In fact, all nonce-verbs created for this study were phonologically similar. They all were disyllabic, had the same syllable structure (CVCVC) and carried the suffix -ek. These properties may have additionally increased the salience of words referring to verbs and facilitated their recognition. Thus, to detect the ungrammaticality of the sentences, participants may have simply relied on the absence of these target properties from the sentence-final word. Finally, learners’ knowledge of the verb placement rule may be tightly linked to the effective learning of verb referents [12, 110]. This seems to be fully in line with previous research demonstrating robust relationship between the development of vocabulary and grammar (e.g., [12, 114–116]).
The GJT results also suggest that, by session 5, participants had developed an at least partial understanding of the noun–adjective word order. However, the learning effects observed were not equivalent for the two language groups. While the L1 German participants responded with above-chance accuracy on sentences containing adjective placement violations (Table 12), the L1 English learners’ performance was not greater than chance (Table 7). Following the above-mentioned claim regarding the relation between vocabulary and grammar, we argue that one likely reason for the difference in accuracy between the two groups may be tied to the better learning of the word-referent mappings for adjectives in the L1 German group (M = 78.1%) compared to the L1 English group (M = 68.9%). A second reason for these results may stem from participants’ previous foreign language learning experiences. While none of the L1 German learners had previous knowledge of additional case marked languages, all of them had learned English and nearly all of them (33/38) had been introduced to either Spanish or French in the school setting (foreign language learning is compulsory in Germany). Importantly, in both Spanish and French, color adjectives strongly tend to occur in post-nominal position [117, 118]. Although none of the German participants included in this study reported working knowledge of any additional languages other than English, it remains possible that their earlier linguistic experience with Spanish or French may have facilitated the detection of similarities between the previously taught languages and Kepidalo, leading to positive transfer effects. Such a possibility would be in line with the idea of lexical and syntactic transfer from L2 to L3 [119–121].
Yet, the learning of the noun–adjective word order was not as effective as that observed for the verb placement rule. We hypothesize that this difference in learning outcomes is directly related to input frequency. Indeed, there is a great deal of research emphasizing the role of frequency in L2 learning [52, 122–124]. Similar to L1 acquirers, L2 learners are sensitive to the frequency of syntactic constructions in the input, and thus, constructions that occur frequently are often more fluently processed than the less frequent ones. In Kepidalo, in contrast to nouns and verbs, adjectives were optional and appeared only in half of the sentences, providing fewer opportunities for learning. This is reflected in the lower learning outcomes for both the referents for adjectives and the noun-adjective word order, compared to the referents for verbs and the verb placement rule. Further support for the role of input frequency comes from the finding that additional exposure to language led to an improvement in L1 German participants’ performance on adjective placement violation trials between sessions 5 and 6.
Finally, further evidence of grammar learning emerges from participants’ responses in the Grammatical Comprehension tests. In particular, throughout the study, participants in both language groups exhibited superior performance on sentences that had the canonical SOV word over those with the non-canonical OSV sentences. This pattern of performance may be linked to the relative frequencies of occurrence of the two word orders in the input. Hence, it is likely that the higher frequency of the SOV word order promoted learning of this pattern. An additional factor that may have contributed to this frequency effect can be traced to the noun pretraining task. Recall that in that task, all nouns appeared in the nominative case only (e.g., Alg-i). Thus, the early presentation of nouns in the nominative case ending might have led participants to memorize these forms as unanalyzable chunks (e.g., Algi) and take them to be the only potential word-forms that can be mapped onto the different referents. Later, the increased likelihood of occurrence of these word-forms in the highly salient sentence-initial position during the lexical training and grammar test blocks may have facilitated their recognition, resulting in higher accuracy on the SOV sentences.
The learning of the canonical SOV pattern can also be taken to reflect a learners’ subject-first preference when assigning grammatical roles to noun phrases in transitive sentences [125–127]. One potential explanation for this preference is that placing the subject/agent before the object/patient allows learners to engage a simple sequential processing strategy for determining the meaning of the sentences. Given the increased complexity of the artificial language, and due to lack of explicit instruction, learners may have adopted this strategy as it is less cognitively taxing than using case marking information [128, 129]. Accordingly, the stronger subject-first preference observed in the initial stages of exposure may reflect learners’ tendency to adopt this strategy, firstly, due to insufficient evidence regarding the presence of a second word order and, secondly, because it frees up more cognitive resources which they can use for processing the sentences for meaning, given that they are still attempting to learn the novel vocabulary.
A further explanation for the better learning attested for the SOV pattern can be linked to L1 experience effects. However, the manner in which these effects emerge are different for the two language groups. First, regarding the L1 German participants, L1 effects may stem directly from the application of L1-based strategies on L2 sentence processing. Native speakers of German tend to exhibit a preference for subject-first (SOV) readings when presented with Noun-Noun-Verb sentences in their L1 [130–132]. Accordingly, similar to our findings, it has been shown that L1 German L2 learners are also inclined to interpret non-native Noun-Noun-Verb strings as SOV [133–135]. On the other hand, the effect of L1 experience follows a more indirect path in the case of the L1 English learners. In contrast to native speakers of German, L1 English speakers usually assign an OSV interpretation to Noun-Noun-Verb sequences in their native language [133, 136]. Thus, the pattern of performance observed here cannot be directly attributed to L1 transfer. Rather, our results appear to be in line with the idea of meta-transfer [137]. In order to determine the grammatical roles of subject and object in a sentence, native speakers of English rely strictly on word order cues. Subsequently, when exposed to a new language, instead of simply employing the English surface word order (i.e., SVO), L1 English learners tend to transfer their sensitivity to word order as the main processing strategy from their L1 to L2. Thus, potential meta-transfer effects are thought to be strongly constrained by input frequency. In this study, the higher frequency of the SOV order as well as the early presentation of nouns in the nominative case may have led participants to abandon their L1-based preferences for SVO, or for OSV, when presented with Noun-Noun-Verb sentences, in favor of the interpretation that was more available, namely SOV. Interestingly, our results seem to corroborate earlier findings from natural language learning studies showing that, in contrast to native speakers of Japanese, L1 English learners of Japanese tend to over-rely on the canonical SOV order [137–139].
Despite our participants’ success with the canonical SOV order, accuracy on OSV sentences in both groups was below chance levels across all sessions in both groups. While factors like input frequency and L1 experience can be used to account for the better learning of the canonical order documented in Experiments 1 and 2, they can equally be employed for explaining participants’ difficulties with the non-canonical OSV order. Indeed, previous studies have shown that grammatical constructions that occur less frequently in the input or share less structural properties with previously learned languages present more processing difficulties for non-native speakers and tend to be acquired later [140–143].
Most importantly, however, the limited learning of the non-canonical word order could be seen as an outcome of participants’ struggles with learning case marking. Results of the GJT in both Experiments 1 and 2 revealed that participants showed a strong tendency to incorrectly accept ungrammatical trials that contained case marking violations (Tables 7 & 11). This appears to be fully in agreement with the well-documented difficulties of adult learners in processing and acquiring L2 inflectional morphology (e.g., [51, 60, 144, 145]).
One of the main sources of these difficulties is thought to be the low perceptual salience of inflectional morphemes [146, 147]. In contrast to most lexical items, morphemes are usually made up of a single segment or syllable, are unstressed, and, due to their word-final position, are often likely to be fused with surrounding items, making them hard to perceive and learn. These low salience effects can be additionally influenced by two factors, namely learned attention and decomposition. The fact that neither English nor German mark the singular nominative and accusative cases on nouns, may have led learners to direct their attention to other L1-related cues for interpretation, instead of attending to case marking. While word order appears to be an obvious candidate for native speakers of English, as mentioned earlier, we suspect that this was also the cue L1 German learners use, at least during the initial stages of learning. Secondly, limitations in adult learners’ decomposition ability [148, 149], may have led participants to treat the novel words as unanalyzable wholes, instead of decomposing them into stems and suffixes, hampering the detection and processing of case marking information. It should, however, be mentioned that, although both language groups experience difficulties in learning case marking, given the marginal use of case marking in English, these are far more pronounced in the L1 English group. In sum, these results seem to further confirm the idea that acquiring L2 morphology incidentally can be particularly challenging for adult learners [11–13, 40], while also demonstrating that such learning difficulties can persist even for learners who have native knowledge of a morphologically rich language.
In light of these findings, the present study joins the handful of previous studies examining the simultaneous learning of word order and case marking [11, 12, 110] in showing that word order is more susceptible to learning in incidental contexts of exposure and, as a result, acquired faster. Importantly, while learned attention and cue salience tend to reduce the noticeability of grammatical morphemes rendering them less learnable for non-native speakers, sensitivity to sequential probabilities is thought to remain available in adults [16, 150], enabling them to extract sequential patterns from structured or unstructured input. Indeed, a number of studies have found a strong association between sequential learning and L2 sentence processing (e.g., [151, 152]). In fact, sensitivity to sequential/temporal cues appears to be pervasive in L2 acquisition. For instance, work on cue weighting in L2 speech perception shows that early L2 learners tend to rely primarily on temporal (i.e., duration) instead of spectral information in order to distinguish between speech sounds [153–155], even in cases where their L1 makes little use of duration [156]. Thus, overall, our findings appear to highlight the important role of sequential processing in L2 acquisition [8, 157, 158].
Another objective of the present study was to examine whether the provision of extensive incidental exposure to input can increase the robustness of novel grammar learning (RQ3). Our results show that despite the improvement in participants’ performance over the course of the study, not all aspects of grammar were learned reliably. Specifically, while extensive incidental exposure was sufficient for learning rules related to surface word order patterns, it was not enough to lead to the acquisition of case marking. Thus, our results echo previous studies evidencing relatively low learning effects for L2 case marking under incidental conditions (e.g., [11, 13]), thereby suggesting that in order for low salient morphosyntactic forms such as inflectional morphemes to be effectively learned by adult L2 learners, explicit types of instruction, as well as sufficient exposure, should be considered basic preconditions [4, 159, 160]. It should, however, be acknowledged that although the training regimen employed here is described as extensive, the amount of artificial language input provided makes up only a limited proportion of the input learners usually receive in naturalistic contexts over an extended period of time. Hence, the observed learning outcomes can only be taken to be reflective of the very early phases of language acquisition.
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