Trends in Usage-Based and Pragmatic Language Processing and Learning: A Bibliometric Analysis on Psycholinguistics and Second-Language Acquisition Studies

This chapter provides bibliometric analyses of novel trends in the research toward pragmatic aspects of language processing and learning in the studies of psycholinguistics and second-language acquisition. Growing interests in the relevant themes are shown with the analysis of the co-occurrence of keywords in a common literature and the bibliographic coupling between literatures. The emer-gence of novel experimental methodologies, including the application of neuroimaging and machine learning approaches to the psycholinguistic research, provides new opportunities of looking into the pragmatic aspects of language acquisition and invites new empirical research to validate the theories and extend the boundaries of second-language acquisition research in the real-world setting.


Introduction
Language is communicated with a purpose. As active users of language, we are intrigued in how lexical choices can be used to represent our minds and bodies; how our mother tongue can shape our learning processes; and how linguistic expressions benefit our social interactions with others. These questions naturally fall inside the issue of the processing and the acquisition of language in the real-world setting (or the usage-based and pragmatic processing and learning). On one hand, in the history of psycholinguistics, only a very small group of studies has these relevant focuses. The empirical evidence and theoretical frameworks for language use in real-world scenarios are scarce. Most asked questions regarding how linguistic expressions are processed [1,2]. Few addressed issues regarding who uses these expressions, and under what context and for what purpose are these expressions chosen. On the other hand, a growing need is foreseen in the field of second-language acquisition studies to combine the theories of L2 acquisition and psycholinguistic paradigm that is developed or adapted to examine the teaching and learning of a second language in the real-world scenarios and to give a higher emphasis to the study of acquisition of pragmatic knowledge in another language. This chapter takes an initiative to provide a quantitative bibliometric analysis on the latest trend in the theme of functional, usage-based, and pragmatic language processing and learning in psycholinguistics and second-language acquisition studies. These trends are partly formed by the successful validation of experimental paradigms and the rapid development of interdisciplinary methods to track the neurocognitive underpinnings related to one's language behavior and will contribute to a greater understanding of how the language is understood, produced, and picked up in the socio-communicative settings.

Bibliometric analysis
According to the principle of the bibliometric analysis, a co-occurrence analysis based on keywords shows the frequency of the keywords that emerge in one article at the same time and how strong the emergences are [3]. The core themes of a research field can be identified by analyzing the links between keywords and by pointing out the most frequently occurred keywords in the field. We aim to use the co-occurrence analysis based on keywords to understand the evolution of main research themes related to the functional and the usage-based language processing and learning in the field of psycholinguistics and second-language acquisition [4]. To explore the relationship between research contexts and knowledge structure underlying the publication, the bibliographic coupling analysis has been employed between related studies that share at least one bibliographic coupling of cited reference. The more citations two publications share, a stronger bibliographic coupling strength between two publications is indicated, suggesting a similarity between the topics and knowledge. The novelty of the bibliometric coupling is that it finds the related research works, groups them into clusters, and builds a bibliometric network based on strength they connect with each other. Here this method demonstrates the core document (strongly and frequently coupled documents) and the core clusters representing the connections to this core document, among the publications relevant to the pragmatic and usage-based language processing and learning.
The first purpose of this chapter is to address the bibliometric trend of psycholinguistic studies on pragmatic and usage-based language processing. Research articles were selected from the Web of Science Core Collection database with the search function TS = (('psycholinguistics' AND 'usage') OR ('psycholinguistics' AND 'function') OR ('psycholinguistics' AND 'pragmatics')). The search function resulted in 95 key articles that cover publication years from 2010 to 2019 (by September 14, 2020). The second purpose is to make a bibliometric analysis on the second-language (L2) language acquisition studies that focused on usage-based and pragmatic language acquisition. Searching within the same database with the search function TS = (('second-language acquisition' AND 'usage') OR ('second-language acquisition' AND 'function') OR ('second-language acquisition' AND 'pragmatics') OR ('L2 acquisition' AND 'usage') OR ('L2 acquisition' AND 'function') OR ('L2 acquisition' AND 'pragmatics')) revealed 601 key articles that cover publications within the 10 years (by January 11, 2020).
All articles were collected in the Science Citation Index Expanded (SCI-EXPANDED), the Social Sciences Citation Index (SSCI), and Arts & Humanities Citation Index (A & HCI) databases. All analyses were performed in BibExcel (Version 2016-02-20 [5]), and network results were visualized in VOSviewer (Version 1.6.13). and pragmatic/usage-based language learning were contributed by 1418 unique authors. The top contributors who authored at least four publications during the past 10 years are Professors Bardovi-Harlig Kathleen (Linguistics), Saito Kazuya (Linguistics), Roumyana Slabakova (Linguistics), Ellis Nick (Psychology), Emanuel Bylund (Psychology & Linguistics), Antonella Sorace (Linguistics), Jason Rothman (Psychology), Silvina Montrul (Linguistics), and Ping Li (Psychology & Linguistics). Authors from 48 countries contributed to the publication. The most productive countries (at least 10 articles) as the first author were the United States (211), England (45), China (34), Germany (33), Canada (33), Netherlands (20), Australia (19), France (19), Italy (15), Sweden (13), Belgium (12), Japan (12), and Korea (10), suggesting that the topics relevant to the pragmatic and usage-based language learning were interested by research groups with expertise in linguistics and/or psychology, and the languages of interest were more various. Besides the Indo-European languages such as English, German, French, and Italian, the East-Asian languages, in particular, Chinese, Japanese, and Korean, are the popular languages of research.
The keywords that appeared at least five times among target publications in the topic of psycholinguistics and pragmatic and usage-based language processing highlighted the following related themes [Language (17), Comprehension (11), Psycholinguistics (10), Speech (8), Speakers (7), Acquisition (6), Information (5), Context (5), and Perception (5)] and methodology [Eye-movements (5) and Children (5)]. In the topic of usage-based and pragmatic language learning, the keywords that occurred at least 10 times among target publications represented the themes highlighting Second Language Acquisition (76) and L2 Acquisition (15), Bilingualism (56), Language Acquisition (23), Spanish (20), Pragmatics (17), Study Abroad (15), Language, (14), Working Memory (14), Second Language (13), English (13), Vocabulary (13), Second Language Learning (12), German (10), Interlanguage Pragmatics (10), and fMRI (10). The comparison of the keywords between these two topics clearly indicates a distinct trend of research interest and methodology of use in the field psycholinguistics and the field of second-language acquisition studies. These trends can be summarized as follows: The former group of studies is interested in comprehension, speaking, and developmental aspects of language and predominantly relying on the online behavioral measurements. The latter group relies more on the neuroscientific methods and focuses on the learning aspects of language and bilingualism.

Pragmatic and usage-based language processing
The co-occurrence analysis conducted on psycholinguistic studies on pragmatic and usage-based language processing revealed nine clusters of 73 keywords (with minimum cluster size set as 5) in total that mutually appear in a pair of target articles over all records based on the search function (see Figure 1). The clusters were ranked in a descending order based on their size and strength of connections. These clusters reflect what readers may rely on to search for the interested articles in the field of psycholinguistic research toward the functional, usage-based and pragmatic language processing (see Table 1 for the list of key words per cluster). The first cluster reflects the trend in examining the processing of patterns and formulaic language usages in L1 and L2 speakers. The second cluster reflects the trend in investigating the usage and representation of formulaic expressions in discourse and conversation and discusses the relevant capacity and cognitive process such as perspective-taking processes. The third cluster reflects the focus on syntactic processing and Broca's area, in sentence comprehension, the ambiguity and interference during language production and their relation with fluid intelligence, interference, and perspective taking. The fourth cluster reflects the trend of using neurocognitive indices (brain potentials and eye-movements) and modeling approach in lexical decision and recognition paradigms. The fifth cluster suggests the trend of focusing on intonation and speech, highlighting indirect languages such as sarcasm and verbal irony and the contextual impact during comprehension. The sixth cluster shows the trends in speech production and the dynamics of activation of representations during the process. The seventh cluster highlights the trend of investigating the cognitive processes (such as categorization, access to the knowledge, perception, and comprehension) in autistic individuals. The eight cluster shows an independent trend of looking at idiom comprehension, the deficits of it, and its relation with working memory. The last cluster reflects some trend focusing on developmental psycholinguistic research.

Pragmatic and usage-based language learning
The co-occurrence analysis conducted on second-language acquisition studies on the pragmatic and usage-based language learning revealed 14 clusters of 296 keywords in total (with minimum cluster size set to 10) that mutually appear in at least a pair of target articles over a consecutive number of records (see Figure 2 and Table 2). The first cluster reveals a strong trend represented by a group of empirical studies on speech and phonological learning with cognitive neuroscience approaches. These approaches included but were not limited to the functional neuroimaging, the eye-tracking, and the recording of other online linguistic behaviors. In this trend, multiple cognitive processes were tapped, and individuals with particular sensory deprivation (e.g., deaf), cognitive impairments (e.g., specific language impairment), or neurodevelopmental disorders (e.g., dyslexia) were included as target populations of testings. The second cluster shows a trend of examining the processing different linguistic aspects (such as morphosyntactic, lexical, gestural, pragmatic, referential, and so on). Under the usage-based framework in both adult and second-language acquisition. The third cluster uniquely represents the trend of investigating the second-language acquisition of various functional and discourse markers, for instance, the usage of definiteness and   Table 1.
Clusters and the list of keywords in the co-occurrence analysis of publications relevant to psycholinguistic studies on usage-based and pragmatic language processing. Clusters are visualized in the co-occurrence map in Figure 1.
specificity, conversational and scalar implicature, functional words, and mood. The fourth cluster reveals a trend of examining the association of individual's cognitive control or executive function abilities (including switching, inhibition, attentional monitoring, and working memory) and other related processes with secondlanguage acquisition. The fifth cluster shows a trend of analyzing the role of instructional and learning strategies in second-language acquisition of pragmatic functions in educational and cultural settings. The sixth cluster reveals a latest trend of studying bilingual language processing and reading with functional and structural neuroimaging techniques, focusing on cross-linguistic comparisons that involve Mandarin. The seventh cluster emphasizes the studies on the interface of syntax and pragmatics and the interface of syntax and discourse, with a target language Spanish and heritage languages. The eighth cluster represents a trend of determining the structure of pragmatic competence and characterizing the role of pragmatic capacities in social interaction and adaptation. The ninth cluster represents the studies on the pragmatic acquisition (e.g., speech act) with English as a second language as a testing case. The 10th cluster focuses on the dynamic interplay between the second language and the first language, emphasizing how the acquisition of a second language may interfere or cause the loss of the capacity of using the first language. The 11th cluster mainly deals with the visual language acquisition, including the sign language and the spatial language. The learning of other syntax-related functions is discussed under the usage-based language acquisition framework in the rest of the clusters (e.g., the topics of null subject, of formulaic sequences, and of word order).

Pragmatic and usage-based language processing
Among 95 articles relevant to the study of psycholinguistic studies on pragmatic and usage-based language processing between 2010 and 2019, 80 shared citing references. According to the shared citations, the articles were clustered into seven groups, with the minimum number of citations per cluster equals to five (see Figure 3 and Table 3). The first group of research focuses on the psycholinguistic experiments on pragmatic functions. The topics includ irony, presupposition,  pragmatics-syntax interface, autism, Parkinson's disease, mild cognitive impairment, executive control training, selective attention, and theory-of-mind. The third group of research concerns conventional expressions and formulaic languages, which includ the topics such as frequency of lexical use and second-language learning. The fourth group of research discusses the flexibility in pragmatic inferences and the relevant topics includ the scalar inferences and counterfactual inferences. The fifth group of research concerns the individual differences in syntactic and pragmatic processing, such as the working memory constraints on syntactic islands and semantic comprehension, and pragmatic strategy in syntactic attachment. The sixth group of research focuses on bilingualism, which covers the topics including code-switching, cross-modal linguistic transfer, phonological processing, and the consequence of bilingualism. The last group of research discusses communicative and pragmatic function of lexical meanings. The topics includ the nounnoun compounds, polysemy, sublexical constituents, and negation.

Pragmatic and usage-based language learning
Among 601 articles relevant to the study on second-language acquisition between 2010 and 2019, 571 shared citing references. According to the shared citations, the articles were clustered into eight groups, with the minimum number of citations per cluster sets to 10 (Figure 4 and Table 4). The first research group highlights the empirical studies on factors that affect different aspects of secondlanguage acquisition in children or young adults, with many involving a comparison between the first-language and the second-language acquisition. The second group of research highlights the acquisition of lexical and grammatical aspects of language in L2, distinguishing the role of domain-general (e.g., the cognitive constraint on frequency learning) and domain-specific factors (e.g., the knowledge of linguistic register) in second-language acquisition. The third group concerns the effectiveness of various instructional strategies (e.g., virtual learning environment) and the perception of teaching strategies (e.g., corrective feedback) in the acquisition of pragmatic competencies. The fourth group concerns the development of pragmatic strategies in L2, for instance, the use of speech acts (such as apology request and refusal acts), prosodic strategies, conversational implicature, quotative marking, and conventional expressions. The fifth group concerns the syntax-pragmatics interface during second-language acquisition. Some special themes are discussed, which include the null and overt subject, wh-question, co-reference and anaphora, and left dislocation. The sixth group of research uniquely focuses on the cognitive  Table 3.

Cluster number
Title of the article 1 A strong link between verbal and emoji-based irony: How the brain processes ironic emojis during language comprehension 1 Accommodating presuppositions is inappropriate in implausible contexts The effect of word predictability on reading time is logarithmic 5 Which noun phrases is the verb supposed to agree with? Object agreement in American English

5
Working memory predicts semantic comprehension in dichotic listening in older adults advantage (especially in the executive function) and the neural consequences of bilingualism, with the aid of neuroimaging techniques. The seventh group aims to examine the factors that affect the second-language acquisition and the firstlanguage attrition in the aspects of syntactic, prosodic, and pragmatic skills (e.g., the age of acquisition, the richness of language input, and the neurocognitive constraints). The last group is devoted to the research on the processing of discourse and pragmatic marker (e.g., the usage of article, scalar implicature, and presupposition) in second-language learner.

Summary and future direction
The bibliometric review shows a growing trend of research interest in the function, usage, and pragmatics of language in the field of psycholinguistics and in the field of second-language acquisition. These trends indicate that the existing The good, the not good, and the not beautiful: on the non-obligatoriness of suppression following negation Table 3.
Clusters and title of articles in the bibliographic coupling analysis on the psycholinguistic literature on pragmatic and usage-based language processing. Clusters are visualized in the bibliographic coupling network map in Figure 3.  Table 4.

Cluster number
Title of the represented articles The relationship between L2 instruction, exposure, and the L2 acquisition of a syntaxdiscourse property in L2 Spanish investigation of language communication and acquisition in real world is still in its infancy and invites further empirical and theoretical contributions. The frequency distribution clearly shows the leading contributors and the journals most attracted to the relevant topic. The co-occurrence and the bibliometric coupling analysis demonstrate that researchers are most interested in the processing of various interpersonal and socio-pragmatic functions in L1 and L2 speakers in the field of psycholinguistics, as well as factors underlying L2 acquisition from children to adults, and the impact of the cognitive and neurodevelopmental impairments in the field of second-language acquisition. One important direction is to combine the real-time neurophysiological recordings (such as eye-tracking, EEGs and fMRI) with the psycholinguistic paradigms for investigating the real-world language use to reveal the neurocognitive architecture underlying pragmatic language processing and those underlying language acquisition (e.g., [6,7] for some reviews). The use of virtual reality to create naturalistic scenarios will be a good complementary approach to test the impact of real-world social interaction on one's language processing and learning [8]. Of special interests is the testing of linguistic phenomena that can be addressed by different categories of communicative functions, such as indirectness (e.g., [9]), presupposition (e.g., [10]), speech/communicative acts (e.g., [11,12]), and politeness (e.g., [13][14][15]), among many others, on both well-represented, dominant languages and underrepresented, marginalized languages (e.g., east-Asian languages such as Chinese, Japanese, and Korean and their dialects) and on one's own and unfamiliar languages [16][17][18][19][20]. These topics are seldomly addressed in psycholinguistic literatures, and the experimental paradigms adapted to address these topics are rare in the secondlanguage acquisition literatures. New computational approaches such as machine learning and computational modeling will provide a solution to the classification of different types of communicative functions in L1 with higher accuracy. However, whether such approaches can reveal the novel feature in the classification of communicative functions in L2 is still an unaddressed question. The capacity of classifying communicative categories in one's second language with the model built in one's mother tongue, and the vice versa, is promising to reveal if the mental representation underlying pragmatic functions is shared or distinct between L1 and L2. Other fascinating lines of research are to enhance the understanding of the individual differences in the processing of pragmatic language that is endorsed by professional, political, or cultural background of the language users [21,22], and the atypical processing that may be revealed by testing individuals with pragmatic impairments or variations (including but not limited to neurodevelopmental and neurodegenerative disordered individuals). With the aid of multimodal approaches to build intelligent recognition system, the profiling for one's pragmatic language ability is likely to provide a novel way to predict or diagnose individuals with special clinical status [23]. It is still unknown how learning a second language can affect Cluster number Title of the represented articles 8 Revisiting fluctuations in L2 article choice in L1-Korean L2-English learners 8 How much do Cantonese ESL learners know about the English article system? 8 The non-generic use of the definite article the in writing by Turkish learners of English Table 4.
Clusters and title of articles in the bibliographic coupling analysis on the second-language acquisition literature on pragmatic and usage-based language learning. Clusters are visualized in the bibliographic coupling network map for Figure 4. Given large numbers of article, only articles that weighed top 10 in each cluster were listed. The articles were ranked in a descending order according to their weights in a cluster.
one's pragmatic language ability in those who suffer from certain clinical status. These new possibilities, combined with what has been indicated from the bibliometric review, will make significant contributions to reveal a new trend in developing new psycholinguistic paradigms for studying the mechanisms underlying the usage-based and pragmatic language processing. Our bibliometric method may be limited in the coverage of literatures given that the literature search was only focused on the published articles in the databases of Web of Science where the journals of these publications are indexed. The nonjournal works such as books, dissertations, and conference papers can also contribute to the latest development in the shift towards pragmatic and usage-based language processing and learning in the relevant fields and could be incorporated for judging the impact of the research. The findings from the present analysis also await verifications from other citation tracking databases, such as Google Scholar, PubMed, and PsycInfo. Despite such limits, the bibliometric analysis provides evidence-based descriptions, comparisons, and visualizations of research output [24] and proposes a promising research avenue at the interface of psychological science, language science, and educational science. In particular, the network analysis and the visualization of the network structure for co-occurring keywords and for co-citing articles somehow serve as the tools to monitor the subject collaboration and to identify the cross-cluster research efforts of high performance and high impacts in the field of psycholinguistics and the field of second-language acquisitions (Figures 1-4). These emerging discoveries and trends invite more dedicated and interdisciplinary research outputs to address the arising issues of the functional, usage-based, and pragmatic language processing and learning in the field of psycholinguistics and second-language acquisition studies.