Introduction

Recent advancements in linguistic research have illuminated the complex dynamics governing language acquisition and proficiency, showcasing the interplay between socio-cultural contexts, educational environments, and individual learner traits. Studies by Yoon (2017) and Leroux and Kendall (2018) accentuate the pivotal role of contextual factors in shaping language learning paths, revealing the interweaving of sociolinguistic influences with cognitive processes that define linguistic competence (Abe, 2015; Caldwell-Harris & MacWhinney, 2023; Evans, 2019; Lange & Leuckert, 2019; Soyoof et al., 2023; Saleem & Saleem, 2023; Zheng, 2016). Building upon these insights, this research investigates the frequency of inflectional morphemes as a foundational element in understanding language acquisition within varied populations of English learners.

Our study focuses on contributing empirical evidence to the ongoing discourse regarding the variations in inflectional morpheme usage within the International Corpus Network of Asian Learners of English (ICNALE) (Leroux & Kendall, 2018; Lim, 2022; Pongpairoj, 2020; Saleem et al., 2022). This exploration serves as a crucial avenue for comprehending the complex landscape of language acquisition and usage among English as a Second Language (ESL) and English as a Foreign Language (EFL) learners. Recent studies by Dong (2023) and Darvin and Norton (2023) accentuate the significance of investigating inflectional morphemes to unravel the intricate dynamics of language acquisition. By scrutinizing region-specific variations within ICNALE and the English as an L1 Speaker (ENS) corpus, our study seeks to unearth the nuances underlying these linguistic landscapes. Further, Mason (2019) emphasizes the need for detailed analyses of morphological features across diverse learner backgrounds, highlighting the influence of cultural and educational contexts on language learning outcomes. Additionally, Kim (2021) stresses the relevance of comparative studies in discerning divergent patterns of inflectional morpheme usage among ESL and EFL learners, advocating for a comprehensive understanding of these disparities to enhance language pedagogy and curriculum development.

Our study bifurcates into two primary avenues: firstly, examining region-wise disparities in inflectional morpheme frequency within ICNALE concerning English L1 speakers, aligning with recent findings indicating substantial variations in language usage among English L1 speakers across distinct geographical regions (Melvin-Brown et al., 2022; Saleem & Khan, 2023). Secondly, our inquiry extends to discerning differences in inflectional morpheme usage between ESL and EFL learners within the ENS context, aligning with studies highlighting the impact of linguistic backgrounds and educational settings on language acquisition patterns among these learners (Caldwell-Harris & MacWhinney, 2023; de Kleine et al., 2022; Saleem et al., 2023).

Through comprehensive investigation and assimilation of contemporary research insights, our study endeavors not only to delineate disparities but also to unravel underlying factors contributing to observed variations. This research significantly contributes to the ongoing discourse on language acquisition, proficiency, and the dynamic interplay between linguistic variations, learner backgrounds, and educational contexts by examining region-specific inflectional morpheme frequencies within ICNALE. Additionally, our exploration of inflectional morpheme orders for different learner groups—ENS, ESL, and EFL—contributes to the discourse on deviations in learners’ usage patterns compared to English L1 speakers, thus enriching our comprehension of language acquisition complexities.

Literature review

Language acquisition and proficiency have long been subjects of keen interest in linguistic research, with recent advancements shedding light on the complex interplay of various factors influencing these processes. Of particular significance is the exploration of inflectional morphology, which forms a foundational element in understanding language acquisition dynamics (Batool & Saleem, 2023). This literature review aims to provide a comprehensive overview of the importance of examining inflectional morpheme frequency, the current state of research in this area, and the gaps that exist, particularly concerning the distinction between English as a Second Language (ESL) and English as a Foreign Language (EFL) learners, as well as the importance of comparing results across different regions.

Inflectional morphology, the study of how words are modified to convey grammatical information such as tense, number, and case, plays a crucial role in language acquisition. Understanding inflectional morpheme frequency provides insights into the linguistic competence of learners and sheds light on their language learning trajectories (Abe, 2015; Batool & Saleem, 2023; Caldwell-Harris & MacWhinney, 2023). By examining inflectional morpheme usage, researchers can uncover the subtle nuances that contribute to variations in language proficiency among different learner populations (Evans, 2019; Lange & Leuckert, 2019; Mushtaq et al., 2021; Saleem et al., 2021; Ullah et al., 2023). The importance of this topic lies in its potential to enhance language pedagogy and curriculum development. By identifying patterns of inflectional morpheme usage across diverse learner backgrounds, educators can tailor instructional approaches to better meet the needs of ESL and EFL learners (Mason, 2019). Moreover, a detailed understanding of inflectional morphology can inform language policy decisions and contribute to the development of more effective language assessment tools (Kim, 2021; Khan et al., 2023).

While there has been significant research on inflectional morphology in language acquisition, there are notable gaps in the literature. One such gap is the limited focus on distinguishing between ESL and EFL learners. While both groups are learning English as an L2, they often face distinct challenges and exhibit different patterns of language use (Dong, 2023; Darvin & Norton, 2023; Haroon et al., 2023). Understanding these differences is essential for designing targeted interventions and support strategies for language learners. Additionally, there is a need for more comparative studies examining inflectional morpheme frequency across different regions. Language learning is heavily influenced by socio-cultural factors, and variations in language usage are observed among speakers from different linguistic backgrounds (Laufer, 2023; Melvin-Brown et al., 2022). By comparing results across regions, researchers can gain insights into how cultural and educational contexts shape language learning outcomes and inform cross-cultural communication practices.

The current study analyzes eight specific forms of inflectional morphemes in English. The selection of these morphemes for analysis was guided by various factors, including their frequency of occurrence, grammatical significance, and relevance to the research objectives. Although English possesses a limited number of inflectional morphemes compared to some other languages, the decision to focus on these eight forms was deliberate, considering their importance in conveying grammatical information. These eight selected forms encompass a wide range of grammatical functions essential to English language usage. They include pluralization, possession, tense marking, and comparison, all of which are fundamental aspects of English grammar (Lieber, 2021). Furthermore, ample literature supports the significance of these inflectional morphemes in language acquisition and proficiency (Abe, 2015; Caldwell-Harris & MacWhinney, 2023; Evans, 2019; Ghani et al., 2022; Lange & Leuckert, 2019; Soyoof et al., 2023; Zheng, 2016).

In light of these considerations, the present study aims to contribute to the existing literature by analyzing region-specific inflectional morpheme frequency within the International Corpus Network of Asian Learners of English (ICNALE). By examining variations in inflectional morpheme usage among ESL and EFL learners from different regions, this research seeks to unravel the complex dynamics of language acquisition and proficiency in diverse linguistic contexts. Ultimately, this study aspires to inform language teaching methodologies, curriculum development, and language policy decisions, with implications for enhancing language learning experiences for learners worldwide.

Research questions

The current study formulated the following research questions:

  1. 1.

    What are the variations in inflectional morpheme frequency across regions when compared to English L1 speakers in ICNALE?"

  2. 2.

    How does the frequency of inflectional morpheme usage differ between ESL and EFL learners in the context of ENS?

Methodology

A quantitative study is crafted to delineate the patterns of inflectional morphemes, utilizing the ICNALE Corpus (International Corpus Network of Asian learners of English). This research is corpus-based, enabling an extensive contrastive analysis due to the accessibility of the online ICNALE. The scope of the study is limited by the nature of data collection in the ICNALE corpus, primarily sourced from interviews and written compositions. While this method ensures standardization across diverse learners, it may also introduce influences from interviewers or elicitation tasks. This serves as both a strength, providing consistency, and a weakness, potentially impacting grammatical features. Additionally, the findings only highlight differences in inflectional morpheme usage across proficiency levels and learner types, without directly linking them to teaching strategies or explaining why certain features manifest at specific levels or among learner groups.

Population

The study focuses on ESL and EFL learners from ten Asian regions: Hong Kong, Pakistan, the Philippines, China, Thailand, Taiwan, Korea, Japan, and Indonesia, all represented in the ICNALE corpus. Sri Lanka was excluded from the study due to insufficient data coverage across proficiency levels; most data were collected from learners at the lower and upper thresholds. The research specifically delves into the interlanguage of Pakistani learners. In Pakistan, English is learned as a second language and has been the official language since 1947 (Saleem et al., 2018). Additionally, English serves as the instructional medium in higher education (Siddiqui, 2016). The inclusion of Pakistani learners made ICNALE a suitable choice due to its diverse data from Asian regions.

Data collection

The International Corpus Network of Asian Learners of English (ICNALE), developed by Dr. Shin Ishikawa, comprises 10,000 topic-controlled essays and speeches from ten Asian regions alongside contributions from English L1 English speakers. ICNALE is structured into four modules: spoken monologue, spoken dialogue, written essays, and edited essays, rendering it the most extensive publicly available learner corpus (Ishikawa, 2019). This study utilizes the ICNALE corpus's spoken monologue and written essays to analyze and delineate trends in inflectional morpheme usage among Asian learners.

Features of ICNALE

The ICNALE project is guided by seven key principles:

  1. i.

    Focus on Asian Learners: Unlike its predecessor, ICLE, which primarily focused on Western learners, ICNALE was specifically designed to cater to Asian learners, addressing the lack of data on this demographic.

  2. ii.

    Varied Modes of Learner English: ICNALE encompasses both written and spoken modes of data collection, enabling researchers to compare monologue and dialogue samples for a comprehensive analysis.

  3. iii.

    Control on Conditions: ICNALE exercises strict control over tasks and conditions, prompting learners to express their views on designated topics. Essays, speeches, and interviews follow predetermined guidelines regarding time, length, and structure.

  4. iv.

    Control of Proficiency: Learners in ICNALE are categorized into proficiency groups (A1, B1-1, B1-2, B2+) based on standardized vocabulary and English proficiency test scores, facilitating a standardized evaluation process (see Table 1).

  5. v.

    Survey of Learner Background: Information about the learners was gathered through a questionnaire covering basic details like gender, age, duration of English study, field of study, and reasons for learning a second language (L2).

  6. vi.

    Collection of English L1 Speaker Reference Data: English L1 speaker data was gathered under identical conditions as the L2 speakers, providing a reference point for comparison.

  7. vii.

    Open Distribution: The ICNALE is openly accessible through two avenues: an online version and a downloadable version.

Table 1 Proficiency levels in ICNALE
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Data sample

During data collection, both English L2 and English L1 speakers were instructed to compose papers under controlled conditions. This involved providing opinions on similar topics within a standardized timeframe, resulting in papers of comparable length, referencing, and use of computer technology. Additionally, the authors' personal attributes, L2 proficiency, learning background, and experiences were extensively examined. As a result, ICNALE gathered data from 10 regions and regions across Asia. However, data from English L1 speakers was not included. The dataset now consists of approximately 1.3 million words. The 1.0 version of ICNALE was released in December 2012, followed by the 2.0 version in January 2013.

Data analysis procedure

To explore usage trends of inflectional morphemes across ESL and EFL learners in comparison to ENS, we calculated the frequency of eight inflectional morphemes within written and spoken corpora. This analysis involved tagging the data using Tree Tagger, a tool designed by Helmut Schmid at the Institute for Computational Linguistics, University of Stuttgart. Tree Tagger annotates text with part-of-speech and lemma information, and it was selected for this study due to its capability to tag all eight inflectional morphemes individually. The tags assigned to these morphemes were used throughout the analysis.

  • Plural: NNS

  • Possessive: POS

  • Comparative degree: JJR

  • Superlative degree: JJS

  • Subject verb agreement: VVZ

  • Present participle: VVG

  • Past participle: VVN

  • Past tense: VVD

The tagged data underwent analysis using Antconc 3.5.8 to assess both frequency and token count. Individual morpheme frequencies were gathered for all regions and normalized per 10,000 words. The spoken and written corpora's total word tokens across regions are detailed in the table below, accompanied by tables and graphs for comparative presentations Table 2.

Table 2 Word tokens of ICNALE
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Results

This section comprises four components presenting the results. The first part explores the frequency of inflectional morpheme usage in ENS, three ESL regions, and six EFL regions. The second part involves a cross-region comparison of the frequency of individual morphemes. The third part focuses on comparing ENS, ESL, and EFL regarding inflectional morpheme frequency. Lastly, the fourth part analyzes Pakistani learners' Interlanguage by comparing various proficiency levels.

Comparison of inflectional morphemes across regions

This component offers a comparative analysis of each inflectional morpheme across different regions, aiming to illustrate which morphemes demonstrate more pronounced variations among Asian learners.

Possessive

This part reports the normalized frequency of possessive inflectional morphemes in written and spoken corpora across various regions is evident (see Table 3 & Fig. 1). The frequency has been normalized to 10,000 words to facilitate cross-region comparisons. Within the spoken corpus, the possessive occurs at a rate of 15.7 times in ENS. Hong Kong and Japan exhibit similar trends, with frequencies of 15.56 and 15.3 respectively. Taiwan and the Philippines follow closely at 14.3 and 14.6 respectively. In contrast, Korea and China demonstrate notably higher values, registering 21.0 and 25.2 respectively. Conversely, Pakistan and Indonesia show lower frequencies at 11.1 and 10.9, while Thailand exhibits an exceptionally low frequency of only 2.2 times per 10,000 words.

Table 3 Frequency of possessive inflections in spoken and written corpora across various regions
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Fig. 1
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Frequency of possessive inflections

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In the written corpus, the Possessive inflectional morpheme value for ENS stands at 19.4, which differs significantly from all other regions. Hong Kong, Japan, Taiwan, China, and Korea display notably high values of 24.6, 26.4, 31.9, and 37.4, while Indonesia, Pakistan, Thailand, and the Philippines demonstrate consistently lower values of 14.6, 13.0, 13.6, and 6.3, respectively.

These values indicate diverse trends in Possessive inflectional morpheme usage across regions in both spoken and written corpora. Although Hong Kong and Japan exhibit a closer trend to ENS in spoken corpus, their values in written text are exceptionally high, suggesting an overuse of this morpheme. None of the regions in the written corpus align with ENS's Possessive morpheme trend. Indonesia, Pakistan, and Thailand show lower values compared to ENS, with the Philippines displaying an extremely minimal frequency. Conversely, Hong Kong, Japan, Taiwan, China, and Korea exhibit markedly higher frequencies.

In the context of L2 acquisition, learners encounter challenges in acquiring the appropriate usage of possessive inflectional morphemes due to the lack of consistent rules or patterns. The divergent trends observed across regions highlight the complexity of mastering possessive morphology in English as a second language. Learners struggle to internalize the correct contexts for using possessive inflections, leading to inconsistencies in their usage across different linguistic environments. Additionally, the discrepancy between spoken and written frequencies in the Philippines suggests that learners prioritize spoken language proficiency over written language accuracy, potentially reflecting differences in language learning contexts or pedagogical approaches.

Comparative degree

This section reports the normalized frequency of the comparative degree inflectional morpheme in written and spoken corpora across different regions (see Table 4 & Fig. 2). The frequency, standardized to 10,000 words, allows for cross-region comparisons. In the spoken corpus of ENS, the comparative degree appears 29.7 times, with Korea and Taiwan exhibiting similar trends at 28.6 and 31.7, respectively. Pakistan and Japan follow with lower frequencies of 24.2 and 21.1, respectively. Conversely, Thailand and China display exceptionally high frequencies at 79 and 54.9, respectively, indicating overuse. Hong Kong, Philippines, and Indonesia also exhibit notably high frequencies at 47.7, 42.2, and 38.9, respectively.

Table 4 Frequency of comparative degree inflectional morphemes in spoken and written corpora across different regions
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Fig. 2
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Frequency of comparative degree inflectional morphemes

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In the written corpus, ENS registers a frequency of 42.8, closely trailed only by Thailand at 42.6. Taiwan and Hong Kong exceed ENS frequencies at 57.7 and 50.1, respectively, while China demonstrates double the frequency, suggesting extreme overuse. Other regions generally use the comparative degree less frequently than ENS. Pakistan, Indonesia, Korea, and Japan follow this trend with frequencies of 27.9, 35.9, 33.4, and 28.5, respectively. Remarkably, the Philippines exhibits a drastically low frequency of 8.6, contrasting with its high usage in the spoken corpus.

A precise rule of L2 acquisition regarding inflectional morphemes, such as the comparative degree, is the tendency for learners to overgeneralize certain morphemes based on their English L1 language patterns to different language registers. For instance, learners struggle with the appropriate use of comparative degree morphemes due to the complexity of comparative structures and the nuances involved in comparing entities. Additionally, the comparative degree poses challenges in mastering irregular forms and comparative constructions, leading to variability in usage across different linguistic contexts.

Superlative degree

This section presents the normalized frequency of the superlative degree inflectional morpheme in written and spoken corpora across different regions (see Table 5 & Fig. 3). The frequency is standardized to 10,000 words for cross-region comparison. In the spoken corpus of ENS, the superlative degree occurs 11.7 times. Most regions exhibit a similar trend, except for Taiwan, Thailand, Indonesia, and Japan. Korea and Taiwan closely align with frequencies of 28.6 and 31.7 respectively, while Pakistan and Japan follow with 24.2 and 21.1 respectively. Thailand and China demonstrate notably high frequencies, leading at 79 and 54.9 respectively. Hong Kong (47.7), the Philippines (42.2), and Indonesia (38.9) also show relatively high frequencies.

Table 5 Frequency of superlative degree inflectional morpheme in spoken and written corpora across regions
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Fig. 3
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Frequency of superlative degree inflectional morpheme in written and spoken corpus across regions

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In the written corpus, ENS records a value of 26.2, with only Thailand exhibiting a similar value of 42.6. Taiwan and Hong Kong surpass ENS with values of 57.7 and 50.1 respectively, while other regions generally show lower values, indicating less usage of the comparative degree among ESL and EFL learners across regions. Philippines (8.6) notably demonstrates the lowest value. Surprisingly, their usage in the spoken corpus is considerably high.

One notable pattern observed in the acquisition of the superlative degree morpheme is learners' tendency to overuse it in spoken language while exhibiting minimal usage in written language. This suggests that learners may struggle with appropriately applying this morpheme in different linguistic contexts. The comparison reveals the superlative degree morpheme as a challenging inflectional morpheme due to its varied usage across regions and modes without a clear pattern.

Plural noun

This section presents the normalized frequency of plural noun inflectional morphemes in written and spoken corpora across various regions ((see Table 6 & Fig. 4). The frequencies are standardized to 10,000 words for comparative analysis. In the spoken corpus, the frequency of plural inflections is 555.6 occurrences in ENS, closely followed by Hong Kong and China at 559.4 and 524.5, respectively. Conversely, Pakistan and the Philippines exhibit higher values, indicating an overuse, while other regions demonstrate less frequent use, with Indonesia having the lowest value at 362.3.

Table 6 Frequency of plural noun inflectional morpheme in spoken and written corpora across regions
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Fig. 4
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Frequency of plural noun inflectional morphemes

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In the written corpus, ENS registers a frequency of 679.4. Korea, China, and Japan exhibit similar frequencies, ranging between 678.2 and 682.2. Conversely, Hong Kong, Pakistan, and the Philippines demonstrate higher values, while Thailand and Indonesia display lower frequencies.

Among the ESL learners, there is an observed overuse of the morpheme in both corpora. In contrast, EFL learners demonstrate optimal use in the written corpus but tend towards underuse in the spoken corpus. This pattern aligns with a common rule of L2 acquisition regarding inflectional morphemes, where learners tend to initially overapply morphemes before gradually refining their usage. For example, ESL learners overuse inflectional morphemes in their written and spoken production as they attempt to apply grammatical rules learned in instruction or through exposure. On the other hand, EFL learners, who have less exposure to English outside of instructional settings, demonstrate optimal use in written contexts where they have more time to deliberate on language production but underuse in spontaneous spoken interactions where real-time processing demands are higher.

Subject verb agreement

In the spoken corpus, the subject-verb agreement inflection occurs 97.6 times in ENS, with the Philippines displaying a similar frequency. Pakistan stands out as the only region showing overuse, while all other regions, particularly EFL nations, demonstrate underuse, nearly half the frequency observed in ENS. This highlights a common challenge for all EFL learners, indicating the difficulty associated with this specific morpheme (see Table 7 & Fig. 5).

Table 7 Frequency of subject verb agreement inflectional morpheme in spoken and written corpora across regions
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Fig. 5
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Frequency of subject verb agreement inflectional morpheme

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Figure 5 depicts the normalized frequency of subject-verb agreement inflectional morphemes in written and spoken corpora across various regions, standardized to 10,000 words for comparative analysis.

In the written corpus, ENS registers a frequency of 80.8, with China and Korea exhibiting similar usage patterns. However, both Pakistan and the Philippines exhibit an overuse of the morpheme in written text. Conversely, all other regions display lower frequencies, indicating an overall underuse of the morpheme.

The findings underscore that subject-verb agreement poses a notable challenge for EFL learners, particularly evident in the spoken corpus where data shows significant deviation from the usage pattern observed in ENS. One notable rule of L2 acquisition regarding inflection morphemes, such as subject-verb agreement, is the tendency for learners to struggle with irregular verb forms and complex agreement patterns. This difficulty often stems from differences between the learner's native language and English, leading to errors in verb conjugation and agreement.

Past tense

In the spoken corpus, the past tense inflection occurs 41.3 times per 10,000 words in English L1 Speaker (ENS) samples, with Taiwan showing a similar trend. Korea and Thailand exhibit an overuse, while all other regions demonstrate an underuse of this morpheme. ESL regions tend to show lower values compared to EFL learners (see Table 8 & Fig. 6).

Table 8 Frequency of past tense inflectional morpheme in spoken and written corpora across regions
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Fig. 6
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Frequency of subject verb agreement inflectional morpheme

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In Figure 6, we illustrate the normalized frequency of past tense inflectional morphemes in written and spoken corpora across various regions. The frequency has been standardized to 10,000 words for comparison across regions.

For the written corpus, the value in ENS samples is 45.1. Pakistan, Indonesia, Japan, and Thailand follow a similar trend, while Taiwan and Korea show an overuse. China and Hong Kong display very low frequency, suggesting difficulty in the use of this morpheme among these learners. In terms of L2 acquisition, one observed pattern regarding past tense inflection is the phenomenon of regularization. This occurs when learners apply regular past tense endings (-ed) to irregular verbs, thereby simplifying the morphological structure. The tendency toward underuse in ESL learners suggests a stage in which learners are still acquiring irregular past tense forms, leading to the overapplication of regular forms. On the other hand, the mixed trend in EFL learners indicate a combination of factors, such as varying degrees of exposure to English language input, differences in instructional methods, or interference from the learners' native languages.

Past participle

In the spoken corpus, the past participle inflection occurs 123.5 times in English L1 Speakers (ENS), with Pakistan exhibiting a similar trend of usage. The Philippines shows a higher frequency, while all other regions demonstrate underuse of this morpheme. There's a noticeable pattern of underutilization among Asian learners in conversation (see Table 9 & Fig. 7).

Table 9 Frequency of past participle inflectional morpheme in spoken and written corpora across regions
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Fig. 7
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Normalized frequency of past participle inflectional morpheme

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Figure 7 displays the normalized frequency of the past participle inflectional morpheme in written and spoken corpora across various regions, with the frequency normalized to 10,000 words for cross-region comparison.

For the written corpus, the ENS frequency stands at 163.6, with Hong Kong, Pakistan, and the Philippines displaying similar frequencies. Conversely, all other regions exhibit underuse, with Thailand recording the lowest frequency, nearly half of the ENS values.

This observation aligns with a common rule of L2 acquisition, where learners tend to struggle with irregular inflectional morphemes such as past participles. They initially rely on regular forms or avoid using irregular forms altogether until they have mastered the grammatical rules and patterns. The ESL learners' adherence to the ENS trend in the written corpus suggests a higher proficiency level or greater exposure to English language norms, allowing for more accurate usage of past participles in written communication.

Present participle

The normalized frequency of the present participle inflectional morpheme in written and spoken corpora across different regions is presented in Table 10 and Fig. 8. The frequency has been adjusted to 10,000 words to enable cross-region comparisons.

Table 10 Frequency of present participle inflectional morpheme in spoken and written corpora across regions
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Fig. 8
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Frequency of past participle inflectional morpheme

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In the spoken corpus, the present participle inflection occurs 177.9 times in ENS (English L1 Speaker) contexts, while all Asian learners exhibit lower frequencies, indicating underuse in their speech. Among these learners, China demonstrates the least frequency.

Regarding the written corpus, ENS registers a frequency of 201.1, with Hong Kong and the Philippines closely trailing this value. However, other Asian regions show even lower frequencies, suggesting an underuse of this morpheme in their writing.

In terms of L2 acquisition, one rule that can be observed regarding inflectional morphemes is the tendency for learners to underuse certain morphemes compared to English L1 speakers. This underuse may be influenced by factors such as the complexity of the morpheme, transfer from the learner's native language, or insufficient exposure to the target language's grammatical structures. In the case of the present participle inflection, the lower frequencies observed among Asian learners in both spoken and written contexts reflect a stage in the acquisition process where learners have not fully internalized the rules governing its usage in English. This highlights the importance of targeted instruction and increased exposure to facilitate the acquisition of inflectional morphemes in L2 learners.

Comparison of ENS inflectional morphemes use with ESL and EFL Group

This section provides an analysis comparing the utilization of inflectional morphemes among ESL (English as a Second Language) and EFL (English as a Foreign Language) groups. For the analysis of data, inferential statistics were conducted. The primary objective is to discern any prevalent trends or distinctive patterns that might differentiate EFL or ESL from English L1 speakers (ENS).

Comparison of spoken Corpus

The comparison of the spoken corpus involved conducting a One-Way ANOVA test. The results revealed that for the inflectional morphemes POS, JJR, JJS, NNS, VVZ, VVN, and VVG, the p-values all exceeded 0.05, which is the conventional significance level (see Table 11). This indicates that there are no significant differences among the groups for these morphemes. However, for the inflectional morpheme VVD, the p-value was 0.10, which is slightly higher than 0.05 but still in proximity. While not statistically significant at the conventional significance level of 0.05, this suggests a marginal indication of differences among the groups for this morpheme.

Table 11 ANOVA results for frequency of inflectional morphemes among ENS, ESL, and EFL Learners in the Spoken Corpus
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Comparison of written Corpus

In analyzing the written corpus, a One-Way ANOVA test was employed to compare the use of inflectional morphemes among the learner groups. The results (see Table 12) revealed significant differences in the use of POS (F(2, 6) = 4.79, p = 0.049), JJR (F(2, 6) = 3.42, p = 0.001), NNS (F(2, 6) = 7.56, p < 0.001), and VVG (F(2, 6) = 2.78, p = 0.029) among the three learner groups. These findings suggest variations in the utilization of these morphemes across the learner groups. However, the analysis did not yield significant differences for JJS, VVZ, VVD, and VVN (p > 0.05). Despite not reaching statistical significance, these results still provide valuable insights into the similarities in the usage of these morphemes among the learner groups.

Table 12 ANOVA results for frequency of inflectional morphemes among ENS, ESL, and EFL learners in the written corpus
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Pairwise comparisons using Tukey HSD tests (see Table 13) revealed that EFL learners demonstrated significantly higher frequencies of POS (p = 0.03) and JJR (p = 0.00) compared to ENS learners. Additionally, ESL learners exhibited significantly higher frequencies of NNS compared to both ENS (p = 0.02) and EFL (p = 0.04) learners.

Table 13 Pairwise comparisons using Tukey HSD tests
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Discussion

The analysis of region-specific inflectional morpheme frequencies within ICNALE presents interesting global linguistic nuances. This study examined the diverse usage patterns across regions, shedding light on how speakers from different linguistic backgrounds utilize inflectional morphemes in English. The findings regarding the normalized frequency of possessive inflectional morphemes across written and spoken corpora in various regions reveal interesting cross-cultural differences. Analyzing this through the lens of research by Abbasi et al. (2023), which examined the acquisition of English grammatical morphemes by young Pakistani Sindhi high school ESL learners, the observed disparities in possessive usage align with their findings. Abbasi et al. (2023) highlight that ESL learners often exhibit variations in acquiring specific grammatical features, which contribute to the divergent patterns seen in possessive usage across different regions. Snape's (2022) study, focusing on L1 Chinese L2 English speakers, particularly resonates with the observed disparities. Snape's (2022) exploration of functional morphology suppliance and the Prosodic Transfer Hypothesis sheds light on how cultural and linguistic backgrounds influence morpheme usage in ESL learners. The higher frequency of possessive usage observed in regions like China can be attributed to the influence of L1 (Chinese) morphological structures transferring into L2 (English) usage, as Snape (2022) suggests. Asadi et al.'s (2023) investigation into children's command of inflectional constructions in Arabic provides a comparative perspective. While their study centers on Arabic, it highlights the developmental aspect of acquiring inflectional morphemes. These findings align with the observed variations across different age groups or proficiency levels within ESL learning contexts. The discrepancies observed between spoken and written corpora across regions align with Snape's (2022) discussion on challenges encountered by Chinese ESL learners. The marked disparity between spoken and written possessive usage, especially in regions like the Philippines, resonates with Snape's (2022) idea of linguistic transfer issues faced by ESL learners from specific language backgrounds. In essence, the diverse trends in possessive inflectional morpheme usage, as highlighted in the presented text, echo the complexity of ESL learning and the nuanced influences of learners' linguistic backgrounds, developmental stages, and cultural contexts, as elucidated by the referenced studies.

When investigating the frequency of the comparative degree inflectional morpheme across various regions, Russak and Zaretsky's examination of morphosyntactic representations among L1 Hebrew and Arabic-speaking 6th graders in EFL written narratives shed light on the disparities noted between spoken and written frequencies across different regions. The varying usage patterns in spoken versus written forms relate to the proficiency levels or instructional emphasis on grammar structures, impacting how learners incorporate these inflectional morphemes into their narratives. Laufer's study on understanding L2-derived words in context and the necessity of complete receptive morphological knowledge provides insights into the challenges faced by learners in using the comparative degree inflectional morpheme across different modes. This difficulty stems from insufficient exposure to diverse contexts where this morpheme is applied, contributing to the discrepancies observed in its usage across spoken and written corpora. Therefore, integrating findings from Russak and Zaretsky, and Laufer's studies reinforces the notion that the usage of the comparative degree inflectional morpheme is intricate and influenced by various factors such as proficiency levels, instructional emphasis, and exposure to diverse linguistic contexts. The disparities observed across regions and modes underscore the complexities in morpheme acquisition among ESL and EFL learners, particularly concerning this specific inflection.

Regarding the superlative degree inflectional morpheme, as outlined in the presented text, underscores variations in usage across different regions and language learners. The findings align with studies on English language acquisition and morphological use among ESL and EFL learners. The investigation by Lou and Ma (2023) examines the morphological words in writing among high-proficiency L1 and L2 English learners, which shed light on the discrepancies noted between spoken and written corpora regarding the use of comparative and superlative degrees. Further, Thane (2023) investigates frequency effects in the production of preterit morphology with state verbs in Spanish second language learners, albeit in a different language context. Nevertheless, their findings offer relevant perspectives on the challenges faced by learners in acquiring specific inflectional morphemes like the superlative degree. Moreover, Russak and Zaretsky (2023) examine morphosyntactic representations in EFL written narratives among L1 Hebrew and Arabic-speaking 6th graders, which provide insights into the observed disparity between spoken and written corpus usage of comparative degrees across different ESL and EFL settings. Findings indicate that the comparative degree inflectional morpheme appears more frequently in spoken than in written forms among various ESL and EFL learners. This trend of overuse in spoken forms and underuse in written forms can be attributed to the perceived complexity of this morpheme. The studies collectively suggest that the comparative degree might pose challenges in acquisition due to its varied usage across regions and modes, lacking a consistent pattern.

In terms of plural noun inflectional morphemes in both written and spoken corpora across multiple regions, the ENS data demonstrates a frequency of 555.6 occurrences, with Hong Kong and China closely following at 559.4 and 524.5, respectively. In contrast, Pakistan and the Philippines display higher values, suggesting an overuse of plural markers. Conversely, other regions exhibit less frequent usage, with Indonesia recording the lowest value at 362.3. However, these findings align with studies like Kim, Kim, and Jo (2022), which explore the role of cross-linguistic morphological congruency and L2 proficiency in L3 acquisition of English plural marking. Insights from Lu and Wu (2022) also support these variations, discussing factors influencing Chinese learners' acquisition of English plurality. In the written corpus, ENS registers a frequency of 679.4. Korea, China, and Japan exhibit similar frequencies, ranging between 678.2 and 682.2. Conversely, Hong Kong, Pakistan, and the Philippines show higher values, while Thailand and Indonesia display lower frequencies. These findings resonate with Rattanasone and Demuth (2023), focusing on Mandarin-speaking preschoolers' challenges in acquiring L2 English plural morphology. Mashaqba, Huneety, and Alshdaifat (2023) also offer insights into grammatical number patterns in Arabic-English bilingual children, potentially contributing to the observed variations. Among ESL regions, there is an observed overuse of the morpheme in both corpora. In contrast, EFL regions demonstrate optimal use in the written corpus but tend towards underuse in the spoken corpus.

The frequency of subject-verb agreement inflectional morphemes, across various regions in both written and spoken corpora, reveals interesting insights when considered alongside recent studies. Slomp's investigation (2023) into the effects of processing instruction on subject-verb agreement acquisition by Spanish-speaking second language learners of English aligns with the trends observed. Slomp's (2023) findings likely resonate with the current findings, especially noting the challenge that EFL learners face in grasping this morpheme. Similarly, Bråthen's research (2023) on the role of cross-linguistic influence in English subject-verb agreement acquisition among Norwegian and Polish adolescents shed light on some deviations seen in the usage patterns across regions. It is plausible that these linguistic influences contribute to the observed variations in subject-verb agreement frequency, as seen in the spoken and written corpora. Moreover, Kpoglu's study (2023) focusing on subject-verb agreement marking by Ghanaian learners of French might not directly correlate, but its insights into morpheme acquisition among learners from an EFL context could provide a nuanced understanding of challenges faced by learners in different linguistic backgrounds. Furthermore, Frimu and Dekydtspotter's research (2022) on inference-based form selection in English L1 and English L2 speakers, particularly regarding subject-verb agreement error detection in French, offers insights into cognitive processes involved in error detection and use of morphemes, although in a different linguistic context. The patterns revealed in Fig. 6, notably the discrepancy between ENS and EFL nations in both spoken and written corpora regarding subject-verb agreement, echo the challenges highlighted in these studies. The consistent underuse by EFL learners, with few exceptions like Pakistan's overuse in certain contexts, emphasizes the complexity and difficulty associated with mastering this specific morpheme in English as a foreign language.

The variation in past tense inflectional morphemes across different regions aligns with findings from various studies in the field of second language acquisition. Vallerossa's work (2022) specifically explores the reflections of multilingual learners on past tense verb morphology. The observations regarding the frequency and variations in the use of past tense inflectional morphemes among ESL and EFL learners resonate with the trends highlighted in Fig. 7. It emphasizes the varied patterns of past tense usage among learners in different linguistic contexts. El Malaki and Zeddari (2023) shed light on the impact of phonological similarity on the acquisition of simple past morphology in second language learners. The underuse and overuse tendencies of past tense inflectional morphemes observed in different regions in the spoken and written corpora might reflect the influence of phonological similarities or differences between the learners' native languages and English, affecting their mastery of past tense forms. Moreover, Luk (2022) discusses how lexical aspect influences the use of past marking among Cantonese ESL learners. The findings highlighted in the text align with Luk's observations, showcasing varying levels of past tense inflectional morpheme usage across different regions, possibly affected by learners' linguistic backgrounds and their interpretation of lexical aspects. Similarly, Yang (2022) explores the acquisition of the English tense-aspect system by Cantonese ESL learners. The trends identified in Fig. 7, indicating underuse in ESL regions and mixed trends in EFL regions regarding the past tense inflectional morphemes, are in line with Yang's research findings, emphasizing the complexities involved in ESL and EFL learners' acquisition of the English tense-aspect system. Overall, the data presented in Fig. 7 regarding the utilization of past tense inflectional morphemes in spoken and written corpora across various regions align with multiple studies, suggesting that the variation in past tense usage among ESL and EFL learners may be influenced by factors such as phonological similarity, lexical aspect, and the complexities of the tense-aspect system in English.

The findings regarding the past participle inflectional morpheme in written and spoken corpora across various regions align with insights from recent studies. Kodner's study (2023) on learning Latin verbal morphology highlights aspects of morphological theory. The observed patterns in the frequency of past participle inflection among English L1 Speakers (ENS) and learners in regions like Pakistan are consistent with the research, demonstrating a comparable trend. Dąbrowska et al. (2023) investigate literacy-related differences in morphological knowledge. The study's findings support the observation of underutilization of the past participle among learners across various Asian regions in both spoken and written contexts, aligning with the disparities identified in the corpus data. Barak et al. (2023) delve into children's production of the English past tense and model variable production. Their insights might shed light on the observed deviations and underuse of the past participle inflectional morpheme among learners in spoken and written contexts, particularly in L2 English-speaking regions. Additionally, Chan and Shirai's work (2022) exploring the role of lexical aspect in second language (L2) acquisition, especially in the present perfect tense, might contribute to understanding the disparities in past participle usage among ESL learners in comparison to ENS, especially in written contexts. The distinctive difference in the frequency of the past participle among Asian learners, especially in comparison to ESL and ENS trends, corroborates the cross-cultural and literacy-related disparities highlighted in these studies. The observed underutilization of this morpheme in spoken and written corpora among learners in Asian regions stands out prominently, emphasizing potential challenges or differences in morphological knowledge acquisition across different linguistic and cultural backgrounds.

As regards the findings of present participle of inflectional morpheme in written and spoken corpora across various regions align with insights from recent studies. The study by Gardner, Branigan, and Chondrogianni (2021) examines the spoken and written production of inflectional morphology among L1 Mandarin speakers of English. It's noted that in the spoken corpus, ENS contexts show a relatively high frequency of the present participle inflection at 177.9 occurrences per 10,000 words. However, all Asian learners, particularly those from China, exhibit significantly lower frequencies, indicating underuse of this morpheme in their speech. Moreover, Zeng, Shirai, and Chen (2023) focus on L1 Chinese learners and their acquisition of the English progressive aspect. Their findings align with the observed underuse of the present participle inflection among Asian learners, emphasizing this trend in language production by speakers from these backgrounds. In contrast, concerning the written corpus, ENS maintains a relatively higher frequency of the present participle inflection at 201.1 occurrences per 10,000 words. Notably, Hong Kong and the Philippines closely approximate this frequency, indicating a similar usage pattern to ENS in writing. However, the study suggests that other Asian regions demonstrate even lower frequencies in their writing, suggesting a consistent underuse of this morpheme in written production across various Asian contexts. The research conducted by Boerma, Wijnen, Leseman, and Blom (2017) investigating grammatical morphology in monolingual and bilingual children provides insight into how language impairment might impact the acquisition and usage of inflectional morphemes. While not directly related to the specific context of L1 Mandarin speakers learning English, it underscores the importance of understanding morphological acquisition and usage patterns, especially among learners facing linguistic challenges. Additionally, Clahsen and Jessen's work (2021) on morphological generalization in bilingual language production, particularly considering the age of acquisition, suggests that the variability in usage patterns of inflectional morphemes might be influenced by when these morphemes are learned and incorporated into one's language repertoire. Overall, the convergence of findings from these studies supports the observation that Asian learners, particularly those from China, tend to underuse the present participle inflectional morpheme in both spoken and written English compared to ENS contexts. This underscores the influence of language background and acquisition on morphological usage patterns across diverse linguistic populations.

Regarding the insights into how different learner groups—ENS, ESL, and EFL—employ inflectional morphemes in spoken language, the recognized order for ENS learners' inflectional morphemes comprises Plural, present participle, past participle, subject-verb agreement, past tense, comparative degree, possessive, and superlative. In reference to Zeng et al.’s study (2023) on L1 Chinese learners' acquisition of English progressive, the order of inflectional morphemes for ESL learners mirrors ENS, but with differences in the positioning of possessive and superlative degree. This aligns with findings that compare ESL learners' pattern with ENS, highlighting similar initial morpheme frequencies but a higher occurrence of the comparative degree, deviating from the typical order. Examining Vyacheslavovna and Il'Inichna's study (2022) on word-formation complexity based on learner corpora, the varied usage patterns observed in EFL learners correspond to the deviations noted in the EFL group. EFL learners showcase increased frequencies in the comparative degree and possessive, paralleling the deviations observed in EFL learners from the typical order of inflectional morphemes. Díez-Ortega and Kyle's study (2023) exploring the development of lexical richness in L2 Spanish learners indicates that ESL learners' tendencies towards overuse of plural and the superlative degree might align with findings suggesting ESL learners' overuse of certain inflections. Conversely, EFL learners' underuse of plural and the superlative degree resonates with their observed pattern of underutilization of these morphemes. Additionally, Kodner's research (2023) on learning Latin verbal morphology and morphological theory might shed light on ESL and EFL learners' divergent use of verb inflections compared to ENS. ESL learners' proximity to ENS in verb inflections aligns with their relatively closer usage patterns, while EFL learners display significant deviations, particularly in overusing possessive and past participle, as noted in the presented text.

The findings regarding the order of inflectional morphemes in English learners align with several studies in the field of second language acquisition and English language learning. For instance, Park's (2023) study on L2 English article usage patterns suggests that learners tend to exhibit different patterns in article usage compared to English L1 speakers. This resonates with the observed differences in possessive and superlative usage among ESL and EFL learners as compared to English as a Native Language (ENS) speakers. Park's (2023) work highlights how learners may diverge from native speaker usage, mirroring the disparities seen in possessive and superlative frequency across ESL and EFL contexts. Moreover, Wang et al.'s (2023) research on linguistic complexity in learners' writing, particularly the effects of speaker types and L1 backgrounds, supports the disparities noted in the use of various inflections among ESL and EFL learners compared to English L1 speakers (ENS). The study sheds light on how different learner backgrounds can influence the frequency and accuracy of inflectional morpheme usage, corroborating the observed patterns in the text. Pinchbeck et al.'s (2022) work on validating word lists representing learner knowledge in EFL contexts underlines the significance of considering learners' knowledge levels. This resonates with the varying frequencies of inflectional morphemes among ESL and EFL learners compared to English L1 speakers (ENS), suggesting that these differences could stem from the learners' varying levels of proficiency and knowledge. Furthermore, Derkach and Alexopoulou's (2023) study on definite and indefinite article accuracy in learner English aligns with the observed trends in inflectional morpheme usage. It emphasizes how learners might struggle with certain inflections, like the underuse or overuse patterns seen in ESL and EFL learners regarding specific inflectional morphemes, such as the comparative degree and past tense.

Conclusion

In exploring region-specific inflectional morpheme frequencies within ICNALE, this study has revealed compelling global linguistic nuances. By scrutinizing usage patterns across regions, it has illuminated how speakers from diverse linguistic backgrounds employ inflectional morphemes in English. Notably, the analysis of normalized possessive inflectional morpheme frequencies across various regions’ written and spoken corpora revealed interesting cross-cultural differences. These disparities align with research emphasizing variations among ESL learners in acquiring specific grammatical features, contributing to the diverse patterns in possessive usage across regions. Moreover, findings related to the comparative and superlative degrees echo complexities in morpheme acquisition, resonating with studies addressing challenges faced by learners in mastering specific inflections. The trends observed in plural noun inflections, subject-verb agreement, past tense, past participle, and present participle usage among different regions and learner groups align with prior research focusing on cross-linguistic morphological congruency, L2 proficiency, phonological similarity, lexical aspect, and acquisition complexities. These findings emphasize the influences of language background, acquisition stages, and instructional emphasis on learners’ morphological usage patterns. Analysis of inflectional morpheme orders for ENS, ESL, and EFL learners correlates with studies exploring deviations in learners’ usage patterns compared to English L1 speakers. The disparities observed in possessive and superlative frequencies align with research suggesting divergences between ESL and EFL learners compared to ENS speakers. Additionally, the proximity of ESL learners to ENS patterns in verb inflections resonates with their relatively closer usage, while EFL learners display significant deviations, particularly in overusing certain morphemes. Further exploration could investigate the impact of specific instructional approaches on learners’ acquisition of inflectional morphemes. Comparative studies across various proficiency levels and age groups within ESL and EFL contexts might provide a nuanced understanding of developmental stages in morphological acquisition. Moreover, conducting longitudinal studies tracking learners’ progress over extended periods could shed light on the dynamic nature of morpheme acquisition and potential factors influencing these patterns. Investigating the interplay between morphological complexity and learners’ cognitive processes might offer insights into strategies facilitating more effective learning approaches. Furthermore, exploring morphological transfer phenomena, considering the influence of learners’ native languages on inflectional morpheme usage in English, could deepen our comprehension of cross-linguistic influences. Comparative analyses across diverse linguistic backgrounds and cultural contexts may unveil additional layers of complexity in morpheme acquisition. In brief, this exploration of region-specific inflectional morpheme frequencies in ICNALE illuminates the multifaceted nature of language acquisition. Future investigations along these lines could contribute substantially to refining pedagogical methodologies, fostering more effective language learning experiences for diverse learner populations.