Unlocking words and fluency: Spaced Retrieval small-scale case study practice with Spanish-speaking A1 EFL adult learners

This small-scale case study explores the impact of Spaced Retrieval Practice (SRP) on vocabulary acquisition and oral fluency in Spanish-speaking A1 EFL adult learners, addressing the need for effective instructional strategies that enhance long-term retention and fluency development. Given the importance of lexical knowledge in oral proficiency, this research aims to determine the extent to which SRP influences Mean Length of Run (MLR), Articulation Rate (AR), and Target Vocabulary Usage. A quasi-experimental design was implemented with eight adult learners enrolled in an A1-level English course. Participants completed a pretest and posttest, during which their oral responses were recorded and analyzed using PRAAT software to measure MLR and AR. Target Vocabulary Usage was also calculated through percentage comparisons. The results indicate that MLR and AR increased significantly (p = 0.015), suggesting that learners were able to sustain speech for longer stretches. Additionally, Target Vocabulary Usage increased, demonstrating a positive trend in lexical recall even though this change was not statistically significant (p = 0.117). A correlation was observed between Target Vocabulary Usage and MLR gains suggesting that Spaced Retrieval Practice likely enhanced vocabulary retention and contributed to oral fluency development, supporting its integration into EFL curricula as a pedagogical strategy for improving speaking skills. Further research is recommended to explore longer interventions and digital retrieval tools.

Introduction

Helping learners speak more fluently in a second language is one of the main goals of English language teaching. As Fillmore (1979) explains, fluency involves speaking at length with minimal hesitation while making full use of speaking time. Yet, for many basic-level EFL learners, limited vocabulary can make speaking difficult and fragmented. As Wilkins (1972) famously stated, “without grammar very little can be conveyed; without vocabulary nothing can be conveyed” (p. 111). This highlights the essential role of vocabulary in enabling effective spoken communication.

Despite the growing emphasis on communication in EFL classrooms, many learners continue to struggle with oral fluency. This often points to gaps in teaching, particularly in connecting vocabulary learning with speaking practice. In many instructional settings, vocabulary is taught in isolation through lists, definitions, or short drills, without ensuring that learners can retrieve and use these words fluently in real-time communication. As a result, students may recognize words passively but fail to incorporate them into spontaneous speech. This lack of connection between receptive and productive vocabulary is well-documented: learners typically have a much larger receptive vocabulary (words they can understand) than a productive one (words they can use) (Zhou, 2010; Webb, 2005). While recognizing a word in context requires familiarity, producing it in speech involves deeper processing, stronger memory traces, and repeated retrieval in meaningful use (Schmitt and McCarthy, 1998). Without targeted support for this transition, learners may hesitate, rely on circumlocution, or avoid using new vocabulary altogether hindering fluency development. Closing this gap requires the integration of strategies that not only build vocabulary knowledge but also foster active recall and use of words in meaningful contexts.

One such strategy is SRP, which encourages learners to recall target vocabulary over distributed intervals, strengthening retention and promoting automatic access. Research shows that SRP reduces forgetting and facilitates long-term learning by reinforcing memory traces (Cepeda et al., 2006; Karpicke and Roediger, 2007; Küpper-Tetzel et al., 2014a). Instead of passive exposure, SRP creates repeated opportunities to retrieve language, making it more likely that learners will use new vocabulary during spoken tasks.

Recent studies also confirm a close link between vocabulary knowledge and oral fluency. Enayat and Derakhshan (2021) found that vocabulary size and depth significantly predict speaking performance, particularly in areas such as fluency, coherence, and lexical choice. Similarly, Behbahani and Kooti (2022) demonstrated that combining SRP with output-based tasks helps learners recall words more accurately and speak with greater ease.

To better understand how vocabulary retention supports fluency, it is important to examine specific fluency measures. MLR refers to the average number of words a speaker can produce between pauses of a certain length usually 0.25 s or more (Towell et al., 1996; Tavakoli and Wright, 2020). A higher MLR suggests that a speaker can sustain longer stretches of speech without hesitation, indicating greater fluency. AR in contrast, measures the number of syllables spoken per second, excluding pauses, and reflects the speaker's tempo and ease of delivery (Kormos and Dénes, 2004). Together, MLR and AR offer a detailed view of fluency in terms of both flow and efficiency.

While SRP has gained recognition for its benefits in vocabulary learning, few studies have examined its direct impact on spoken fluency using quantitative indicators like MLR and AR. Understanding this relationship is particularly relevant in beginner-level instruction, where students often lack both lexical depth and speech fluency.

In response to the limited focus on fluency development in traditional EFL classrooms, this small-scale case study intends to explore the effectiveness of SRP in promoting oral fluency among adult A1 Spanish-speaking EFL learners. The intervention integrated repeated and varied retrieval of target vocabulary through interactive class activities. Learners engaged in word search puzzles, anagram-solving tasks, matching exercises, image labeling, guided writing frames, and online audio-based quizzes. These tasks were strategically distributed over a 4-month period and revisited across different contexts (oral, written, visual, and auditory), to reinforce long-term lexical retention. By incorporating SRP into classroom routines through accessible materials, the study aims to examine the extent to which target vocabulary usage changes after SRP intervention; how this technique influences learners' MLR and AR; and the relationship between vocabulary usage and fluency after the intervention.

Review of literature

This section examines the theoretical and pedagogical foundations of Spaced Retrieval Practice (SRP) in relation to vocabulary acquisition and oral fluency in basic adult English as a Foreign Language (EFL) learners. The review begins with core constructs of oral fluency, followed by vocabulary acquisition and vocabulary learning strategies, and concludes with SRP, its theoretical underpinnings, the spacing and lag effects, the forgetting curve, and spacing schedules.

Oral fluency

Oral fluency can be understood as the ability to convey a message clearly and effectively through continuous, coherent speech that maintains the flow of interaction (Oberg, 2013). Segalowitz (2010) conceptualizes fluency as comprising three interrelated dimensions: cognitive fluency, which refers to the efficiency of mental processing needed to formulate utterances; utterance fluency, which captures observable temporal features such as pausing, hesitations, and self-repair; and perceived fluency, which is based on listeners' subjective evaluations of how fluent a speaker sounds.

Because utterance fluency represents the observable expression of language in real time, it is commonly assessed through quantitative temporal measures. Among the numerous indices proposed in the literature, this study focuses on Mean Length of Run (MLR) and Articulation Rate (AR), which provide meaningful information about the rate and continuity of speech during production tasks. Table 1 summarizes the formulas used to calculate these measures.

Table 1

Table 1. MLR and AR assessment.

Given that both indicators are influenced by the ease and speed of lexical retrieval, the next section addresses vocabulary acquisition and its role in oral production.

Vocabulary acquisition

Vocabulary, or lexis, refers to the words of a language and the ways in which they can be combined to express meaning within that language (Stone, 2023). Vocabulary acquisition is commonly described as a process that involves three main components: pronunciation, which concerns how a word is articulated; meaning, which refers to understanding what a word signifies; and usage, which involves knowing how to use a word appropriately in context (Payne, 2024). Schmitt and McCarthy (1998) further emphasize that vocabulary learning extends beyond memorizing word forms and meanings; it also requires understanding how words function in real communication. This process is therefore crucial for effective communication and literacy development, enabling learners to both comprehend and express ideas accurately.

In a second language (L2), vocabulary acquisition differs from first language (L1) development because learners already possess a conceptual and semantic framework based on their L1. Wu (2012) notes that L2 vocabulary learning involves mapping new lexical items onto an existing conceptual system. When the L1 and L2 are closely related, this mapping can facilitate learning, whereas greater linguistic distance can increase the difficulty of acquiring and using L2 vocabulary.

Researchers also distinguish between receptive and productive vocabulary knowledge. Receptive vocabulary refers to words that learners can recognize and understand when they are heard or read, while productive vocabulary refers to words that learners can actively use in speech or writing (Zhou, 2010). Learners typically acquire words receptively before they can use them productively, through both intentional and incidental learning. Over time, receptive vocabulary tends to remain larger than productive vocabulary.

Empirical work suggests that vocabulary learning tasks in many instructional contexts emphasize receptive knowledge. Webb (2005) notes that common activities include consulting dictionaries, matching words to definitions, or inferring meaning from context. In contrast, productive tasks such as cloze exercises or writing activities occur less frequently. Nevertheless, receptive vocabulary plays an important role in overall language development: it is stored in the mental lexicon for future use and serves as a key indicator of general ability and literacy (Christensen et al., 2014; Yunus et al., 2016). Because productive lexical access is essential for oral fluency, it is important to consider how learners apply strategies to acquire, consolidate, and retrieve vocabulary.

Vocabulary learning and acquisition strategies

Vocabulary learning techniques (VLT) are typically regarded as a subset of broader Vocabulary Learning Strategies (VLS) (Nation, 2001). VLS encompass the activities and approaches that learners use to acquire, retain, and apply vocabulary (O'Malley et al., 1985; Rabadi, 2016; Rubin, 1987). Cameron (2010) describes these strategies as deliberate efforts to understand and remember lexical items. Schmitt and McCarthy (1998) argue that any activity that influences how learners acquire or use vocabulary can be considered a vocabulary-learning strategy. Over time, researchers have proposed a range of taxonomies to capture the diversity of such strategies (Gu and Johnson, 1996; Nation, 2001; Schmitt and McCarthy, 1998; Stoffer, 1995).

Oxford and Crookall (1990) classify vocabulary learning techniques according to the degree of contextual support they provide (see Table 2). Decontextualizing techniques present words outside any meaningful context, which may make it more difficult for learners to understand and recall how these words are used in real language. Semi-decontextualizing techniques offer some contextual cues and associations, whereas fully contextualizing techniques embed words within authentic communicative situations. Adaptable techniques, such as structured reviewing, can be combined with any of the other types to reinforce learning.

Table 2

Table 2. Vocabulary learning categories.

While learners may use a variety of strategies, research on long-term retention has increasingly highlighted the benefits of repeated, spaced encounters with vocabulary items. This line of work leads to the concept of Spaced Retrieval Practice (SRP).

Spaced retrieval practice

SRP is a learning strategy in which encounters with vocabulary occur at spaced intervals, and learners are required to actively retrieve previously learned information rather than merely restudy it (Latimier et al., 2021). Retrieval after a delay induces greater cognitive effort than immediate review, strengthening encoding and promoting long-term consolidation (Goossens et al., 2013; Krishnan et al., 2017). Multiple studies demonstrate that spaced retrieval produces more accurate and durable retention than massed learning, in which items are reviewed rapidly after exposure (Namaziandost et al., 2020; Noor et al., 2021). Because fluent speech depends on rapid lexical access, SRP represents a promising pedagogical tool for vocabulary-supported oral fluency in EFL contexts.

Theoretical foundations of spaced retrieval practice

Three major theoretical accounts explain the learning gains associated with SRP: deficient processing theory, encoding variability theory, and study-phase retrieval theory.

Deficient processing theory argues that when information is reviewed under massed conditions, retrieval is too easy and thus processed superficially, resulting in weak retention. Delayed retrieval, by contrast, requires greater cognitive effort, increases attentional engagement, and promotes more durable storage (Koval, 2019).

Encoding variability theory proposes that when retrieval opportunities occur at different temporal moments, the learner engages diverse encoding processes, generating multiple representational pathways. These varied memory traces increase available retrieval cues and improve the likelihood of successful recall (Kornell, 2009).

Study-phase retrieval theory suggests that learning is strengthened when review occasions require true retrieval rather than recognition. Retrieval conducted under challenging conditions, such as delayed intervals, deepens consolidation, while massed repetitions lack sufficient difficulty to reinforce long-term memory (Bell et al., 2013).

Together, these perspectives explain how SRP enhances retention: by requiring effortful recall, promoting varied encoding episodes, and reinforcing memory representations through repeated retrieval attempts.

Spacing effect, lag effect, and the forgetting curve

The effectiveness of SRP is commonly explained through three closely related cognitive principles. The spacing effect demonstrates that learning improves when encounters with material are distributed over time rather than concentrated into massed blocks, a finding robustly supported in experimental and meta-analytic research (Cepeda et al., 2006). Building on this principle, the lag effect specifies that retention is greatest when retrieval attempts are separated by sufficiently long intervals to allow partial forgetting, thereby requiring deeper cognitive reconstruction during later recall (Küpper-Tetzel et al., 2014a). These principles directly counter the forgetting curve, first observed by (Ebbinghaus 1885), which illustrates the rapid decline of memory following initial learning (see Figure 1). By triggering retrieval at strategic intervals, spaced practice interrupts memory decay, strengthens neural representations, and supports durable long-term retention (Vlach and Sandhofer, 2012).

Figure 1

Figure 1. Memory retention by elapsed time (days). Retrieved from Play it Again: The Master Psychopharmacology Program as an Example of Interval Learning in Bite-Sized Portions by Stahl et al. (2010), CNS Spectrums, 15(8), 491–504.

Building on this understanding of spaced learning, the next subsection addresses how different spacing schedules have been conceptualized in the literature.

Spacing schedules

Within SRP research, spacing is conceptualized in terms of absolute and relative spacing. Absolute spacing refers to the number of repetitions distributed across the learning period, while relative spacing concerns the temporal configuration of intervals between repetitions (Karpicke and Bauernschmidt, 2011). Three primary relative spacing schedules are described in the literature: expanding spacing gradually lengthens intervals over time, uniform spacing maintains constant intervals, and contracting spacing shortens intervals between repetitions (Nakata, 2015).

Empirical comparisons of these schedules have yielded mixed findings, with no pattern consistently outperforming the others in vocabulary retention (Karpicke and Bauernschmidt, 2011). Some research suggests that expanding schedules may theoretically align with the lag effect by progressively challenging retrieval as intervals lengthen (Nakata, 2015). However, the broader literature emphasizes that the key determinant of learning gains is not the specific pattern but the presence of spacing itself and the cognitively effortful retrieval it induces. Delayed recall strengthens encoding and consolidation, outcomes that align with the spacing effect and counter the forgetting curve. Accordingly, evidence converges on the view that retrieval opportunities distributed over time outperform massed exposure in supporting long-term retention (Noor et al., 2021).

Pedagogically, spacing schedules inform decisions about how often lexical items should reappear across lessons, tasks, and assessment cycles. Structuring SRP-based review opportunities at deliberate intervals provides a principled rationale for reinforcing vocabulary acquisition and supporting fluent speech production in EFL learners.

Method

This section introduces the methodological framework employed in this small-scale case study to examine the effectiveness of SRP on vocabulary acquisition, aimed at improving oral fluency in Spanish-speaking A1 EFL learners. The instruments, procedures, ethical considerations and samples are presented in detail in the following subsections.

This study adopts an exploratory approach due to its sample characteristics and is framed within an explanatory sequential design, which is widely used in applied linguistics to examine cause-and-effect relationships when random assignment is not feasible (Dörnyei, 2007). Specifically, a within-subjects approach was implemented, whereby participants served as their own control group, allowing for direct comparison of pretest and posttest results. Given the small sample size, the study used the Wilcoxon signed-rank test, a non-parametric statistical method suitable for paired comparisons when normality assumptions are not met (McDonald, 2014).

Instruments

The oral pretest and posttest served as the main instruments to collect oral samples to measure participants' vocabulary knowledge and oral fluency before and after the intervention. Both tests consisted of 10 open-ended questions designed to elicit target vocabulary usage, and responses were subsequently analyzed to determine the percentage of target vocabulary produced and the extent to which these lexical items were integrated into their speech. Two core indicators of oral fluency were calculated from the speech samples collected during the pre-test and post-test phases: Mean Length of Run (MLR) and Articulation Rate (AR). MLR refers to the average number of words produced between pauses that meet a defined threshold, whereas AR indicates the number of syllables spoken per second, excluding pauses. These measures provided a quantitative assessment of speech fluency and delivery speed.

To calculate the percentage of target vocabulary usage, all interviews were transcribed to identify both the total word count and the number of words corresponding to the vocabulary explicitly taught during the intervention (see Annex 1 for the complete list). The proportional calculation was carried out through a rule of three, where the total word count of each interview represented 100 percent, and the number of target vocabulary items produced formed the corresponding percentage. Participants' oral responses to the 10 pre-designed questions were also recorded during both the pretest and posttest phases. These recordings were later examined using the audio-analysis software Praat in order to extract the numerical data necessary for the calculation of MLR and AR.

Praat software (acoustic analysis)

Praat is a free, open-source software program widely used in linguistics to analyze and synthesize speech (Boersma and Weenink, n.d.). In this study, it was employed to extract data related to speech segmentation, including pause duration, total phonation time, and the length of uninterrupted runs. These values were subsequently used to calculate MLR and AR for comparative analysis between pretest and posttest results. In line with criteria commonly used in L2 fluency research, a run was defined as a continuous stretch of speech articulated without hesitation, while a pause referred to any silent interval lasting 0.25 s or longer (Tavakoli and Wright, 2020). Pauses shorter than 0.25 s were considered part of the same run, whereas pauses exceeding this threshold triggered segmentation into separate runs (see Figure 2).

Figure 2

Figure 2. Praat software (Acoustic Analysis). Text grid of Praat analysis of the student's speech sample, visualizing pauses and speech runs during the pretest. The spectrogram displays the waveform, pitch (blue line), and intensity (green line). The segmentation highlights the duration and distribution of speech runs and pauses (Boersma and Weenink, n.d.).

Based on these operational criteria, each speech sample was segmented into separate runs to determine the total number of runs, the final word count, and the total phonation time required to compute MLR and AR. The criteria used to identify valid runs and countable words were adapted from established fluency frameworks (e.g., Skehan, 2003) and were slightly adjusted to account for typical features of beginner learners' speech, including isolated words, self-corrections, and incomplete utterances (see Table 3). These procedures ensured that both the segmentation process and the measurement of fluency indicators reflected the linguistic profile and developmental characteristics of the participants involved in this study.

Table 3

Table 3. Parameters for speech runs and final word count considerations.

To obtain the descriptive statistical analysis of the pretest and posttest results, the mean, median, and standard deviation were calculated. After this initial step, DATAtab (2025a,b,c), an online statistical calculator, was used to conduct inferential statistical analysis. The calculator generated four normality tests: Kolmogorov-Smirnov, Kolmogorov-Smirnov with Lilliefors correction, Shapiro-Wilk, and Anderson-Darling as well as a Quantile-Quantile (Q-Q) plot to visually confirm whether the data followed the expected distribution. Although the normality tests indicated that the data did not significantly deviate from a normal distribution, the Q-Q plot suggested slight skewness (see Annex 2). Taking this into consideration, and given the small sample size, two non-parametric procedures were applied to analyze the data: the Wilcoxon signed-rank test and the Spearman correlation test.

Procedure

Data collection in this small-scale case study was carried out in three stages: oral pretest administration, application of SRP-based retrieval activities during class sessions, and oral posttest administration. In the first stage, participants were recorded while answering 10 open-ended questions (see Annex 3). The questions were delivered in a continuous sequence, and each participant responded to all items before the next one was presented.

In the second stage, learners engaged in SRP-based vocabulary retrieval activities at the beginning of every class. Sessions took place on Tuesdays and Thursdays from 12:15 to 14:15, between November 26, 2024 and January 28, 2025. Throughout this period, participants completed a total of 24 instructional hours using the first seven units of the textbook Top Notch Fundamentals A by Saslow and Ascher (2015). It is important to note that, due to the December holiday season, no classes were held between December 13, 2024 and January 6, 2025; therefore, students were not exposed to the retrieval strategy during that time.

The SRP intervention was delivered exclusively by the teacher, rather than through automated applications, in order to ensure systematic, consistent and contextualized review of the target vocabulary items. All practice materials were designed based on ongoing class observations related to students' overall progress, and adapted to meet the instructional needs emerging throughout the course. Because the review sessions were teacher-led, the SRP activities were adjusted to fit the class schedule, and therefore did not follow the spacing intervals described in previous studies such as contracting, expanding, or equal spacing formats (Nakata and Elgort, 2020; Küpper-Tetzel et al., 2014b; Gerbier et al., 2014; Kang et al., 2014).

The complete set of SRP activities during the intervention and their schedule is presented in Table 4.

Table 4

Table 4. Schedule of the spaced retrieval activities administered.

In the final stage, participants were recorded while answering the same 10 open-ended questions used in the pretest (see Annex 3) following the same sequential response format. The recordings obtained during this posttest were then analyzed to compare performance before and after the intervention. To determine the impact of the SRP activities, the pretest and posttest results were examined quantitatively, focusing on changes in target vocabulary usage, Mean Length of Run (MLR), and Articulation Rate (AR) (see Table 5).

Table 5

Table 5. Data collection results.

Ethical considerations

This small-scale case study adhered to strict ethical standards to protect participants and maintain research integrity following established ethical guidelines for research involving human subjects, such as those outlined by the American Educational Research Association (2011). Institutional consent was secured in writing to ensure alignment with policies and support for this study. All participants signed informed consent letters outlining the purpose of the study, procedures, and voluntary nature, while participants under 18 required parental or guardian consent. Participants were informed of the voluntary nature of their involvement in the research project. The research design minimized any potential harm by employing a supportive environment and standard educational activities. Upon completion, participants received a summary of the findings in an accessible format, ensuring transparency and appreciation for their contributions. These measures align the study with ethical research practices and foster stakeholder trust.

Sample

The target population for this small-scale case study consisted of students enrolled at Escuela de Formación Integral Cordillera (EFI) aged 18–30, most of whom were undergraduate students at Instituto Tecnológico Superior Cordillera. These students take English courses at EFI to meet the A2.2 language certification requirement, which is a pre-requisite for obtaining their degree.

The initial sample comprised 10 A1.1-level learners who were selected through convenience sampling based on their availability to participate. However, due to unclear audio recordings of two students' oral performance during the pretest and posttest phases, the final sample was reduced to eight participants. Classes were held on Tuesdays and Thursdays, and the group presented an equal gender distribution, consisting of four male and four female students.

The table below presents the raw data collected from pretest and posttest assessments of students' performance in three key areas: Target Vocabulary Usage, MLR, and AR. The data highlights individual student performance using SRP before and after the intervention.

Analysis of the results of target vocabulary usage

The Wilcoxon Signed-Rank Test comparing Target Vocabulary Usage between the pretest and posttest showed an increase in vocabulary integration, with the mean rising from 23.13% (SD = 9.57) to 27.52% (SD = 4.58). The median also increased from 21.08% to 27.37%. However, the difference was not statistically significant (W = 9, p = 0.117). Despite this, the effect size (r = 0.45) is considered medium (see Tables 6 and 7; Figure 3).

Table 6

Table 6. Descriptive statistical analysis on Target Vocabulary Usage.

Table 7

Table 7. Wilcoxon Signed-Rank Test analysis on Target Vocabulary Usage.

Figure 3

Figure 3. Bar chart: Target Vocabulary Usage. The bar chart compares the Target Vocabulary Usage in the pretest and posttest. The posttest shows higher mean and median results.

Analysis of the results of MLR

The descriptive statistics for MLR revealed an improvement in students' oral fluency following the intervention. The mean MLR increased from 1.38 words per run (w/r) in the pretest to 2.19 w/r in the posttest. Similarly, the median MLR rose from 1.38 w/r to 2.19 w/r. Additionally, the standard deviation decreased from 0.72 in the pretest to 0.23 in the posttest (see Table 8; Figure 4).

Table 8

Table 8. Descriptive statistical analysis on MLR.

Figure 4

Figure 4. Bar chart: Mean Length of Run (MLR). The bar chart compares the mean and median of MLR in the pretest and posttest.

The Wilcoxon Signed-Rank Test on MLR showed a W value of 2, which is below the critical W value of 6. This result suggests a statistically significant improvement in MLR from the pretest to the posttest (W = 2, p = 0.015, r = 0.79). There was also a large effect size (r = 0.79) (see Table 9).

Table 9

Table 9. Wilcoxon Signed-Rank Test analysis on MLR.

Analysis of the results of AR

The mean of the AR increased from 1.23 w/s in the pretest to 2.04 w/s in the posttest. The median also showed an increase from 1.25 w/s to 2.04 w/s. Additionally, the standard deviation decreased from 0.65 in the pretest to 0.22 in the posttest (see Table 10; Figure 5).

Table 10

Table 10. Descriptive statistical analysis on AR.

Figure 5

Figure 5. Bar chart: Articulation Rate (AR). The bar chart compares the mean and median of the AR in the pretest and posttest.

The Wilcoxon Signed-Rank Test for AR showed a W value of 2, which is below the critical W value of 6. This result suggests a statistically significant improvement in AR from the pretest to the posttest (W = 2, p = 0.015, r = 0.79). There was also a large effect size (r = 0.79) (see Table 11).

Table 11

Table 11. Hypothesis Wilcoxon Signed-Rank Test on AR.

Correlation between target vocabulary usage and MLR

The scatter plot indicates the correlation between Target Vocabulary Usage (%) and MLR. The x-axis represents the percentage of Target Vocabulary Usage, and the y-axis shows the MLR. The trend line, with the equation y = 2.3662x + 1.5351, depicts a positive linear relationship between these two variables. As Target Vocabulary Usage increases, the MLR also tends to increase (see Figure 6).

Figure 6

Figure 6. Scatter plot of Target Vocabulary Usage and MLR. Each pair of dots represents an individual, showing the relationship between Target Vocabulary Usage (%) and MLR.

The Spearman correlation coefficient (r = 0.36) between Target Vocabulary Usage (%) and MLR indicates a moderate positive relationship between the two variables, proposing that higher use of target vocabulary tends to be associated with longer speech runs. However, the p-value (p = 0.382) is above the common significance threshold (p < 0.05), indicating that the correlation is not statistically significant (see Table 12).

Table 12

Table 12. Spearman correlation between Target Vocabulary Usage and MLR in the posttest.

Correlation between target vocabulary usage and AR

The scatter plot shows the relationship between Target Vocabulary Usage (%) and AR. The x-axis represents the percentage of Target Vocabulary Usage, while the y-axis shows the AR. The regression equation y = −0.8549x + 2.274 indicates a negative trend, meaning that as the use of Target Vocabulary increases, the AR slightly decreases (see Figure 7).

Figure 7

Figure 7. Scatter plot of Target Vocabulary Usage and AR. Each pair of dots represents an individual, showing the relationship between Target Vocabulary Usage (%) and AR.

The Spearman correlation test between Target Vocabulary Usage (%) and AR resulted in a negative correlation (r = −0.32), suggesting a moderate inverse relationship between these two variables. This means that as the use of Target Vocabulary increased, AR tended to decrease slightly. However, the p-value (p = 0.435) indicates that this correlation is not statistically significant (see Table 13).

Table 13

Table 13. Spearman correlation between Target Vocabulary Usage and AR in the posttest.

Discussion

The present small-scale case study examined the role of SRP in supporting Spanish-speaking A1 EFL learners' vocabulary acquisition leading to oral fluency development. The findings suggest an indirect connection between SRP and Target Vocabulary Usage, MLR and AR.

Despite the improvement in Target Vocabulary Usage, it was not statistically significant (p = 0.017), both MLR and AR increased in a significant way (p = 0.015) after the intervention.

Target Vocabulary Usage rose from a mean of 23.13% in the pretest to 27.52% in the posttest, and the median increased from 21.08% to 27.37% with a medium effect size (r = 0.45). This suggests that repeated retrieval strengthened learners' accessibility to newly learned words, enabling greater integration of target vocabulary during spontaneous speech.

In contrast, the oral fluency measures showed more noticeable gains: MLR improved from a mean of 1.38 w/r in the pretest to 2.19 w/r in the posttest, and the median from 1.4 w/r to 2.19 w/r with a large effect size (r = 0.79), and AR rose from a mean of 1.23 w/s in the pretest to 2.04 w/s in the posttest, and the median from 1.27 w/s to 2.07 w/s with a large effect size (r = 0.79). This suggests that learners were able to produce longer stretches of continuous speech, likely because strengthened lexical access reduced interruptions caused by lexical searching.

The observed enhancement in MLR and AR aligns with the deficient processing theory, which posits that increased cognitive effort during retrieval strengthens attention and supports memory consolidation. The variety of spaced, engaging activities used in the intervention likely fostered encoding variability, providing multiple contextual cues that support more flexible recall and production. Furthermore, the significant improvements in oral fluency suggest that the retrieval tasks posed sufficient difficulty to promote deeper consolidation, consistent with the Study-Phase Retrieval Theory, which emphasizes that retrieval challenge enhances long-term retention. Collectively, these findings support the view that SRP may work by increasing cognitive effort, diversifying encoding contexts, and involving desirable difficulty, thereby explaining the positive impact on vocabulary retention and oral fluency.

The correlation analysis offered further insights. There was a moderate positive association between Target Vocabulary Usage and MLR (r = 0.32), suggesting that learners who used more target vocabulary tended to produce longer fluent runs, although this correlation did not reach statistical significance (p = 0.382). In contrast, no meaningful association was found between Target Vocabulary Usage and AR (r = −0.32, p = 0.435), which is consistent with prior research indicating that AR is also influenced by factors beyond vocabulary knowledge, such as cognitive processing speed, automaticity, and individual speech patterns (De Jong et al., 2015; Rodgers et al., 2013).

While the study provides useful insights, certain contextual factors should be taken into consideration: the limited sample size and the absence of a control group. Both factors were directly related to students' willingness to participate, as only learners who provided informed consent were included, and recordings from other students were not considered. While this ethical requirement ensured that participants voluntarily participated in the study, it also restricted the possibility of working with a larger group or establishing an experimental control condition. These constraints limit the generalizability of the findings and make it difficult to isolate the effects of SRP from other instructional influences. Finally, this study focused on only two fluency measures (MLR and AR); incorporating additional ones in future research could provide a more comprehensive understanding of how SRP contributes to oral fluency.

Conclusion

As vocabulary development plays an important role in oral fluency (Tong et al., 2022), it is necessary to implement effective vocabulary learning strategies in the EFL classroom. This study examined the way SRP relates to vocabulary acquisition and changes in Target Vocabulary Usage, MLR, and AR among Spanish-speaking A1 EFL learners. The findings showed that although Target Vocabulary Usage increased from the pretest to the posttest, the change was not statistically significant, while it was for MLR and AR. There was also a positive and significant correlation between Target Vocabulary Usage and MLR, but no significant relationship between Target Vocabulary Usage and AR. AR showed no significant correlation as it is a measure influenced by other factors as demonstrated by De Jong et al. (2015) and Rodgers et al. (2013). Overall, the study highlights the importance of further research on SRP, particularly with larger samples, longer interventions, and diverse fluency measures, to clarify its role in supporting vocabulary growth and oral fluency in EFL contexts.

Data availability statement

The raw data supporting the conclusions of this article will be made available by the authors, without undue reservation.

Ethics statement

The study adheres to strict ethical standards to protect participants and maintain research integrity following established ethical guidelines for research involving human subjects, such as those outlined by the American Educational Research Association (2011). Institutional consent was secured in writing to ensure alignment with policies and support for the research. All participants signed informed consent letters outlining the purpose of the study, procedures, and voluntary nature, while participants under 18 required parental or guardian consent. Participants were informed of the voluntary nature of their involvement in the research project. The research design minimized any potential harm by employing a supportive environment and standard educational activities. Upon completion, participants received a summary of the findings in an accessible format, ensuring transparency and appreciation for their contributions. In addition, this project was reviewed and approved by the School of International Studies for ethical purposes, and since it was conducted as educational research within classroom settings, it was considered exempt from IRB approval. These measures align the study with ethical research practices and foster stakeholder trust. The studies were conducted in accordance with the local legislation and institutional requirements. The participants provided their written informed consent to participate in this study.

Author contributions

TD-B: Conceptualization, Formal analysis, Investigation, Writing – original draft, Writing – review & editing. LS-V: Conceptualization, Investigation, Writing – original draft, Writing – review & editing. PS-V: Conceptualization, Investigation, Writing – original draft, Writing – review & editing. AC-F: Conceptualization, Investigation, Supervision, Writing – original draft, Writing – review & editing. MF-H: Writing – review & editing.

Funding

The author(s) declared that financial support was not received for this work and/or its publication.

Conflict of interest

The author(s) declared that this work was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

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